I think it all comes down to a fundamental disagreement we have on what makes for a good, challenging gameplay. The way you're talking makes it sound like you're planning to try at least a portion of your game solo - why else would versatility for one specific character be so important? This is a four-character gameplay setup - the fact that my PC can do only this number of things means the other members of my team will be all the more important. I think that's cool, and gives me a lot of really awesome choices. It also means that rogues and warriors aren't interchangeable and you have to actually think about team composition rather than assuming your PC can handle anything and everything thrown at them.
I get that you dislike the way DA2 changed the gameplay setups; I just don't think it was a bad move on Bioware's part.
Not at all. What I despise is the hammering of characters into concrete, unchangeable "roles" instead of being characters. I want to take a person along because I want to take them along - not because I'm forced to because I need those concrete "roles" in order to play effectively.
Let's just look at Shale, who has multiple different skill trees - damage (melee), damage (range), tanking, and support. If I need her to take some heat, I can do that. If I need her to pelt something from range, I can do that. It opens up all sorts of tactical possibilities.
Rogues can be pretty effective at range as well as in melee, as can warriors. Mages have a ton of different abilities to use, making them a wonderful utility class.
Now take a gander over at DA2:
Want a healer in DAO? Wynne or Morrigan can serve, and so can the Warden as a mage.
Want a healer in DA2? You're stuck with Anders. Bethany is gone at the start or end of Act 1 regardless. Merill can't do it, and Spirit Healer with a Mage PC removes your offensive options entirely.
Warriors? You now have no range options whatsoever. The maps are all tinier than DAO making range a bit less useful, but being able to switch to a range weapon was a nice option. Now you can't, even if you wanted to.
Rogues? Two weapon options, that's it. Daggers and bows, and nothing else. Except that one DLC axe. Anything longer than a dagger is no go, and all the crossbows in the world except for Bianca disappeared in the Fifth Blight. Even if you wanted to have both range and melee options, you can't - no weapon swapping in combat.
In DAO, it's possible to beat the game using pretty much any combination. In DA2, you're much more limited. DAI doesn't seem to be changing that, but actively punishing you for even thinking about it. Each character is good at one thing, and only one thing, and they can never be good at anything else. The eight slot limit is going to murder utility characters, unless, of course you want to save and reload before battles. That's tedium, not tactics.