I'd also argue that they can contribute to party DPS quite well with a 210 potency Stone III and AoE Aero and holy. I also think assize and tetragammon are wonderful abilities that compliment their kit, despite a bunch of very vocal WHM saying how they are terrible abilities (They are wonderful abilities, period.)
Decide Final Fantasy XIV Healer recommendations
JUST MY TAKE, the OP asked for opinions so here is mine and what I have experienced.
Outright the most powerful direct heals. They are the gods of actual healing. Benediction = 0-100% heal which has amazing synergy with dark knight on super heavy pulls. They get divine seal which is +30% potency to all heals every minute (so it has 1/4th uptime), a ton of HoT power through regen, dome HoT thingy, medica 2. I'd also argue that they can contribute to party DPS quite well with a 210 potency Stone III and AoE Aero and holy. I also think assize and tetragammon are wonderful abilities that compliment their kit, despite a bunch of very vocal WHM saying how they are terrible abilities (They are wonderful abilities, period.)
PERSONAL OPINION: In a heavy hitting dungeon/raid this is your go-to healer to get through it. They can heal everything.
Pros: incredible HoT output, incredible direct healing.... NOTHING can compare to their direct healing
Cons? BIG POINT- MANA MANAGEMENT, however in high tier raiding EXPECT a Bard/MCH to be present at any given moment- they restore your mana and trivialize this issue. Aside from regens (which ARE when stacked STUPIDLY potent) they lack any debuffs to prevent damage. But do not underestimate their raw HoT power now!
I will add that I have many WHM friends that would slap me across the face for emphasizing mana management problem, a good WHM will know WHEN they can blow mana and what aiblities to use to juice the most out of their mana. WHM mains are not ignorant and are able to manage their mana and blow people out of the water with their heals.
My main class that I have mained since it's release. I have been through it's lows (when it was considered shit and you'd be removed from a FC for daring to go scholar, I would know )
This class is based 100% on you knowing fights. You have cooldowns such as Eye for an Eye (120s) which reduces damage taken by tanks, and virus which is a single target damage reduction basically. You also have a giant dome that reduces damage taken by 10% as well. Furthermore you have a lot of shield power through aldoquium and succor (single target and aoe heal + shield respectively). You also have a fairy to assist you in healing that you can macro specifically to do specific chores for you. My fairy at ilevel 179 healed for 1291 and myself with 400 potency physic healed for 2701, to give you rough comparison of numbers. We can temporarily boost fairy healing by 40% using "Rouse" a pet buff. It is useful but it will not tip you over the edge as some may suggest.
But alas Scholar is far from this "godlike" thing some people rant on and on about. That heal + shield? Aldoquim has a potency of 300 for the heal. Cure 1 (ONE) has a potency of 400 for comparison. Aldo produces a 300 heal and 300 shield. Succor produces a 150 heal and 150 shield. To give you a comparison to WHM their regen ability (level 35) is a HoT that heals for 150 potency, their dome HoT heals for 100 potency. It is true that now we finally can convert shields to heals, but that is on a 30 second cooldown. In other words, white mage stomps and craps fire on our direct healing output. Instead we need to manage our fairy at all times properly or we risk being thrown under the bus as we spam a 400 Physick spell to top people off.
Also aetherflow is one of our core mechanics and you will see this noted strongly as an argument in favor of scholar. And it is true that this is a favorable situation, however realize this grants "3 free abilities" every 60 seconds. We can either (1) drain mana from a target restoring our own (2) use a healing AoE spell with a potency of 400 (NOT SHABBY!) (3) we can use a 600 potency direct heal. (As comparison cure 2 heals for 650 and while costing mana is spammable if a situation should warrant). But do realize that once you blow through these 3 aetherflow stacks they are GONE and you do NOT have access to these abilities whatsoever in any capacity until you generate another 3 aetherflows. There have been many situations where I have been a DPS witnessing a scholar blow their aetherflow stacks and then my team wipe a raid because they didn't save indominability (the aoe heal). These. Abilities. Are. Not. Free. Do not let anyone misguide you into thinking they are. They are strong but they are tethered and chained strongly down.
In terms of DoE DPS I can confidently say we can do it, although realize Bane (our primary AoE move) costs an aetherflow stack. Remember directly above? Yes, it comes at a premium price for us. It's all pick and choose here. I could go into more and more details, having mained this class for so bloody long, but here is a short thing;
PROS: Mana management, strong damage mitigation tools, strong ability to restore mana without needing a bard (but with a bard this is trivialized in higher tier raids!), is probably "the outright master of trash dungeons" when you overgear. Because let's be serious, if you overgear a dungeon your fairy can heal through it. But this is OVERGEARED STRONGLY.
CONS: Absolute trash in the wrong hands, as I have witnessed myself countless times when I go DPS. But in the right hands it is extremely useful. AoE healing got a boost, for certain, but play WHM immediately after scholar and tell me how you feel. (I play with many WHM and their AoE healing farts and poops fire on what I can do).
Oh and I will state here. Double scholar is VERY DIFFICULT EVEN NOW with the extra abilities. It was brutal in ARR and even now it is an ineffective combo. 2 WHM > 2 SCH. A scholar is best in a high level raid when paired with a different healer otherwise you step on eachothers feet. AKA, virus and antbodies generated, eye for an eye + deployment tactics, all our shields DO NOT STACK and REPLACE. Fairy buffs DO NOT STACK AND INSTEAD REPLACE. So that is probably the biggest drag about this class, no high tier raid wanting to min/max their group would ever consider taking 2 SCH. They will take a SCH and AST, or a SCH or WHM or a WHM and WHM or an AST or AST but a SCH + SCH? No, they do not play well together. I speak from personal experience when it feels like we are dancing together and stomping on eachother's toes.
New class that most people seem to do horrifically with but I've played with some and it's been some of the most pleasurable playing experiences I've had so far. I do not main it, but I do plan on leveling it up.
My takes as a SCH who has paired with a few.
-Their healing potencies are SIMILAR to WHM but WHM is higher, and WHM gets a lot more options such as their 60s 30% cure potency buff for 15 seconds I mentioned above. Furhtermore WHM gets a lot more HoT power. However they get access to very similar abilities like medica is similar to helios, aspected helios is similar to medica 2. They have a cure 2 equilvalent. But that being said I do not feel that they come close to the sheer raw healing output of a WHM, they aren't THAT far off and they CERTAINLY DO BEAT A SCHOLAR IN RAW HEALING (I don't care who flames me for this, it's what I have seen time in and time again at i179. Their raw healing craps on mine similar to WHM.).
-They can aspect to do shields like scholar or spam HoTs like WHM and I think they are quite effective in either task. They are versatile with urinal or diurnal sects, making them able to meld to any party composition.
-Card system.... provides them with a multitiude of buffs. I personally despise RNG but with their higher level skills like royal road and shuffle and hold (? is that the ability name? It's similar to that) they become much less RNG and much more strategy based because you can get rid of garbage you don't want and dramatically improve the chance of you getting what you want.
They can do AoE damage reduction on the party for sure through cards, as well as celestial opposition which is a very underrated move at present. They can boost the entire party's damage by 5% (NOT INSIGNIFICANT WHEN MULTIPLIED OVER 8 PEOPLE! NOT INSIGIFNICICANT!), they can reduce black mages mana costs which is a HUGE deal for fire spammers, they can reduce their OWN COOLDOWNS (! SO UNDERRATED RIGHT NOW) with a card. They can increase the potency of their buff cards. I feel that the card system is a major asset.
-The card system and my brief thoughts on it above.... I feel that the astrologian is hands-down THE "offensive" healer. Scholar does NOT get the same offensive buff capabilities. (If your read deep into scholar we get a fairy buff for 30s that raises party speed by 3%. AST gets the ability to spam cards to much bigger effects though! Much much bigger.)
-With time dilation you can increase ANY BUFF (ANY bUFF) on the target by 15seconds. Absolutely never EVER underestimate this. Have you ever seen a fully buffed out DPS with things like blood for blood, eagle eye, and whatever else and a card get this move cast on them? THIS. MOVE. IS. GAME. CHANGING. PERIOD. In an organized group you can either make a tank godlike for an extended period of time or make a DPS absolutely ridiculously bursty for LONGER periods of time. This move is so underrated now it blows my mind. Celestial opposition is in a similar boat, but is only 5 seconds instead of 15.
And thus another ability furthering my argument that the AST is THE offensive healer.
Also you can pair this 90s cooldown time dilation and 150s cooldown celestial opposition with your OWN card (USE IT ON YOURSELF Before HAND IF YOU GET IT) THE SPEAR (Reduces target's action recast time (non-GCD) by 20%. Duration: 20s ). Doubled potency = 30% cooldown reduction on these abilities.
Let me go into detail and have a basic example, ifrit has nails that spawn and this is a DPS check. Burst them down (ignoring mechanics for example's sake) fast as you can.... use this buff on your highest-DPS-output (dragoon? ninja?) who has all their buffs out and watch them go haywire.
Let me give you examples of buffs:
-Dragoon +15% critical strike chance
-Blood for blood, eagle eye, invigorate, raging strikes, and all the other billion over-cross-classed-skills for DPS
-Scholar selene 3% buff to ASPD
A SCHOLAR AND WHITE MAGE CAN NOT AND WILL NEVER BE ABLE TO DO THIS. Thus I strongly argue that the astrologian is the offensive healer and the best healer to take for DPS check heavy fights. Used PROPERLY (and I see few use AST properly at all).
-Furthermore I feel synastry is also underrated, while no-doube tethered by cooldown it is able to let the ast trivially heal the offtank and tank at the exact same time which IS (despite many criticisms) much more effective than a scholar's fairy healing. Remember my fairy only healed statically for 1.2k, and my 400 potency physic healed for 2.7k. Synastry is a powerful and versatile move. Am I saying it is OP? Do not get me wrong, no. But it is another feature of the AST.
PROS: The offensive healer, played right can certainly heal off content, able to mesh BEAUTIFULLY with WHM or SCH. ie: It is better than WHM + WHM or SCH + SCH and an AST + AST WORKS! It works! One goes into urinal sect the other into diurnal and it just flat out works. They have more raw healing power than scholar by far.
Cons: No access to virus (WHM can get basic version) or eye for an eye (whm can get access to basic version). So therefore no debuffs for the enemy targets. Similar to WHM they are mana intensive, but I'd argue more mana intensive at present because I have seen many AST (even good ones) go OOM. White mage doesn't seem to go OOM as fast. Perhaps it is just new players? But I have observed this. Keep in mind, yet again, a Bard/MCH at high level will greatly offset this demand on yourself.
White mage heals directly more than you
Scholar mitigates damage more than you
BUT you can do either role (both I'd argue) / both roles at the same time better than either can. AKA, you can directly heal stronger than scholar and provide weaker shields. AKA, you can provide damage shields better than WHM and you can provide strong but weaker heals. It is odd to say and that statement will get me backlash but it is the truth. Let me clarify in absolution incase someone misunderstands:
Direct heals: x
Direct heals: x
Direct heals: x
Shields: (nope, nada)
So my personal feel is AST is versatile and a jack-of-all-trades class that is THE go-to offensive healer if played properly. Most people however are learning and are far from tapping into it's full potential. That being said it does a lot of things decently but it does NOT out mitigate scholar and it does NOT out heal WHM who is the absolute KING of raw heal output. But just because it doesn't trivialize the other two healers in their domains doesn't make it weak, it means that if played properly you can maximize what you DO have from both classes + your own flavor with offensive buffs to be effective.
I know AST is going to be my next class I level purely for this reason. High high skillcap but I'd argue the reward when played properly makes the effort to learn worth it. The numbers ARE there already, the skills ARE there already. It is a matter of people realizing how and when to utilize these things.