I don't understand why people get so worked up about a small change like the ability slots. Sure, it's annoying, and if - what we do NOT know - it was made with console gameplay in mind at the expense of PC gameplay it would be even more annoying, but it's really a small thing in the end.
As for the whole combat gameplay, watch Jesse Cox' video. He makes good use of both combat modes and gets through whole areas without having to restock at a camp. He even attacked a rift with no healing potions and two damaged characters.
I don't like everything about the combat. It's still too fast and some of the silly, over-the-top animations from DA2 are making a return. I don't like it but it's not critical, so I'll shrug and move on since I fully expect the many things that look great about DAI will more than make up for these small flaws. Not that I'll keep silent about them, but they are, in the end, small.
@Shaggywolf:
I could go on and on about how much I hate DA2's cross-class combo system. When combination effects became limited to cross-class, I stopped liking them. In ME3 they worked well because there were only two and you didn't depend on specific power setups to create them. In DA2 they did depend on specific power setups and didn't make any sense on top of it. Also, that this went into the rationale for the slot limitation doesn't make sense, because if one character can create them at all, you can't prevent that by limiting the slots.
Even that, though, is a small thing. Shouldn't matter too much in the bigger scheme of things