I also liked the combat in DAO, but it's the one aspect of the game you enjoyed most - really? Not the story or the characters, not the themes or that feeling of being part of a small band of adventurers in a grand, epic plot?
And it makes me wonder why you'd even buy DAI if the thing you like most about the original game is a technical aspect - it's like buying a sequel because you liked the graphics and art style of the original. You can tell it's probably gonna be similar, but they won't just give you the exact same thing over and over again, and that's good, because you already can have the exact same thing over and over again just by playing the original.
Also, I don't think you even can switch out abilities during combat. Think of it like readying spells before combat - there's strategy to it.
Plus, there's a lot of build discussion in the Classes & Builds forum, so there's gotta be something to it all.