DA2's differences from DAO's combat are mostly in feel, not in mechanic. I mean, just look at the animation for Cone of Cold in both games. Even 60 hours into DA2 I looked forward to watching that animation every time I casted that spell. The differences in graphics and presentation make combat feel more action-y and exciting by having lots of visceral action happening on the screen.
Furthermore DA2 mostly relies on dozens of weak enemies, while DAO preferred fewer numbers of stronger enemies. This makes combat FEEL faster because you're plowing through mooks at a hundred miles an hour instead of having to stop whenever a group of darkspawn appear, even though combat sequences in DA2 are actually longer on average than they were in DAO.
And as for the "dumbing down" thing, what they're talking about is the fact that friendly fire was removed from settings easier than Nightmare difficulty. DAO had friendly fire on Normal difficulty and higher. It's true that it makes combat simpler to manage, though I'm not sure the complexity friendly fire gave DAO is the right kind of complexity. Friendly Fire didn't actually make the game have more depth, it just forced you to wrestle with the friendly AI to get anything done.
(Besides, why are the guys who complain about "dumbed down" games playing on a setting lower than Nightmare?)