Class reactions based on just reading tooltips...
Overall
DOTs that aren't associated with Combos have been removed from most classes. Thank goodness. Figuring out where to fit those in around your debuff combo was annoying. I am not going to miss those.
From simply looking at all the numbers, it feels like AOE damage has be nerfed across the board, especially at lower levels. Lvl 60/70 content feels like it'll be fine, numbers-wise, but I've got a list of classes that I'm not going to be playing at lvl 50 (or lower) if I can help it.
In compensation, it looks like single-target damage is slightly better then it used to be...
Thoughts about my mains...
Summoner
The first thing I want to say about Summoner is that at Lvl 70 it feels like it will be fine. I really don't have a problem with where it will be there especially when it comes to single-target damage. AOE damage could be better given that we can't spam AOE damage in the traditional sense, but the single target damage will be fine.
But when it's not at Lvl 70 though... that is going to suck. Especially when it comes to synced dungeon content. Summoner is one of the last classes to get their AOE abiltiy (Dragoon and Ninja are the only jobs to get it later) and it sucks. Majorly. To compare this to the other Mage AOEs, Fire II does 80 potency with no damage fall off and Red Mage's Scatter does 100 potency with no damage falloff. If you were to use Bane on 6 mobs, the first tick of damage would be the potency equivalent of doing Fire II on 3 mobs. And that's it for specificly AOE damage. All your other stuff is single target damage.
To put this in perspective, the next AOE ability that is remotely spamable is Painflare that that's 200 potency with no damage falloff It's also the only Summoner AOE ability that does not have damage falloff. In order for Fester to be better then Painflare, there needs to be 4+ targets (so at least 5 mobs in total) AND the spread DOTs need to be on the targets for at least 15 sec. If neither of those conditions are fulfilled, it's better to use Painflare then Bane and just manually cast Bio+Miasma on mobs. The only really redeeming feature of Bane is that it's radius is larger then Painflare's radius...
Meanwhile, the Ruin family of spells is way more important then it used to be. If you were going to just cast DOTs and leave the enemy alone vs spam Ruin, it would take longer to do the damage as just DOTs then as Ruin spam. The basic takeaway I'm getting is the not using Ruin cuts your damage in half. Summoner is now less of a DOT class and much more of a mobile Ruin spammer then before (Ruin II is still instant-cast).
The class really only starts becoming more viable for synced dungeon content in Lvl. 52+ content when Painflare is gotten which is when the AOE finally does something. It's also when Dreadwyrm Trance is gotten, without which the job really doesn't work anymore as so much damage can only be done while in it.
The thing with Summoner that really sets it apart from the other classes and probably makes it really hard to balance is that it really wants long fights to do max DPS. A main reason being that it's DOTs only do full damage if they can tick for the full 30 sec duration and most mobs aren't alive that long. The most important reason though is that they really need at least 60 sec to get into DW trance and twice that long to bring out Bahamut. So for long Trial/Raid bosses, their damage is comparable to everyone else's 'cause they can actually bring out their entire rotation. However, the long ramp-up time means that they're not going to be doing well when it comes to shorter fights. Flat damage skills are always going to do better, which is what Black Mage and Red Mage have in spades. And the bad news is, Arcanists are going to be stuck with all their low-level skills for ages.
My biggest complaint is that I can't think of any class that's now more frustrating to level or do synced content with then Summoner. It's easily FFXIV's "max this out and never look back" class. And I kinda don't like it that there's a class that's at such a disadvantage when playing old content.
But does it look fun to play at Lvl 70? Oh yes... Bahamut is out in his full glory, but not often enough to make summoning him feel "normal". We've got procs now, but those are really sane procs compared to other classes and fit in everywhere. Lvl. 70 is going to be fun.
Astrologian
Oh my... the changes to this one were lovely. One of the biggest frustrations I had with Astrologian was when I got a card I didn't want to play at the time and the only thing I could do with it was throw it away. And now... extra healing or damage! I also like how Lighspeed interacts with Critical Benifics. Astrologians like building Crit anyway so Benific crits often enough that it shouldn't feel too clunky.
And then there's Sleeve Draw which is just brilliant and will be so fun to play with...
Dark Knight
I like the direction they took this class. They've still got the whole "I'm in two stances at once" thing going for them while also giving them good reasons to get out of Grit on occasion. And now people will maybe finally figure out they need to stay in Darkside as much as possible. The MP regen only stopping in battle is a really nice QoL fix.
Honestly, I'm not a fan of most gauges as I have a "save it for later" mentality about resources (which means I usually don't use them when I soul). But this is definetly the most straightforward gauge out of all the tank classes as far as how it's filled/used. Then again, the other tank classes have a more straightforward stance system that consumes the gauge, so there you go.
Also really like how they've kept the whole absorb MP/HP from your target aspect. I miss that on the other tanks now. And Bloodspillar... just... DPS move while in Tank stace... what more is there to say.
As for other stuff...
I've been messing with the DPS classes and unless I supper like Samurai, I'll probably be fiddling with Dragoon or Ninja. Monk is way too restricting for me to like. Dragoon has a fairly rigid rotation too, but not as much and they've got enough oGDCs to make it interesting. And they've pretty much got the meele version of Atunement stacks and Dreadwyrm Trance now, and I've been juggling that for ages. Ninja is really flexible once you get a system for memorizing the murdra's down, and that's fun.