IMO DA2 combat > DAO combat > DAI combat
I felt that DA2 improved the combat in almost every way. The fatal flaw was encounter design and enemies spawning out of thin air. The lack of tac-cam was a bit of a bummer but I didn't find it that bad.
But DA2 made every class feel fun and important on the the battlefield. It wasn't like DAO where mages were absurdly more powerful than other classes and cross-class combos where a mage-only thing. I think a lot of people are forgetting that DAO had some serious balancing issues. There were many spells/talents/etc on both extremes of the useless vs overpowered spectrum. Often times unlocking a good spell required unlocking three other skills that you would never use. We even had entire specializations like Ranger and Shapeshifter that were trash, especially compared to ridiculous specs like Arcane Warrior.
I still really enjoyed DAO's combat though. I thought the tactics, strategy and planning made up for the slow gameplay. I like setting things up so I don't need to provide too much direct input. Ideally I'm only jumping in to drop a glyph or heal someone or direct attacks at a certain enemy. DAO was really good with that and it's a shame that DAI seemed to throw it away.
Now I like DAI, but I have almost nothing nice to say about the combat, at least on PC. No click to move, god awful tac-cam, no drag-select for party members, no tactics, no auto-attack at launch. There's this really annoying encouragement on playing one character and letting the AI do it's thing. Like if I'm playing a warrior or a rogue I have to navigate my way into my enemy's hitbox and start hacking away. Now that would be fun in an action game, but as much as DAI tries it isn't an action game. There aren't any fancy combat animations or quick fights, the enemies have more health so the same sword slash animation gets pretty tedious over the course of 100+ hours. I literally can't finish my DW rogue or warrior inquisitors because it's so tedious.
As for healing. I'm not really against the idea of getting rid of healspam, there's potential for fun tactical and strategic stuff. But they just didn't really do that, they swapped healspam for guard/barrier spam which I believe is even worse. While we did have easy healing in DAO, the combat wasn't designed completely around it. We had sustainables, buffs, unlimited potions, etc. We could make a bunch of non-mage parties that relied on killing before being hurt and used pots in a pinch. In DAI, EVERYTHING is built around guard and barrier, half the damn buffs and passives in the game are related to improving your barrier/guard. It is almost necessary to have a mage with barrier and a warrior who can build guard. So yeah, congrats you got rid of healspam but replaced it with something that severely damages party diversity and still requires spamming.
Funny enough, I don't really thing the 8 ability limit is a problem in DAI. I've never felt like I really needed a ninth skill. Even if I look at DA2 and DAO, I can't really think of more than 8 skills that I absolutely must have. Maybe in Awakening, but that destroyed DAO's balance anyway.