I'm (wishfully) thinking, from the top of my ignorance, this w/ the radial menu is to incentive strategy, well-thought tactics balancing mindless pew-pew-pew. It's just new to what we've grown accustomed to and might take some adapting to, but not necessarily a horrible thing. Some will like/hate it, other won't care less. Can't really say anything until I've actually played it myself.
I mean, the game has been play tested to exhaustion. If this was such a huge gap & breaking the experience in any way, it'd been reconsidered and "fixed", at this juncture. Makes me think it's on purpose, and as such for the best. Instead of: all I need is a tank, a healer, DPS... etc, at any given situation, more like:
Going into this battle. I'll be doing dmg (map accordingly), while Solas will provide support this time around. Or a mix. We might need more crowd control (map away). And so forth. Each or some of these combat scenarios might require different strategies, as opposed to, this is my char's hot bar for the entirety of the game, if I need something else, there's the radial menu. I don't know if I'm making any sense. And I'm sure there may be times where I'll go "dangit, didn't see this coming & wish I had mapped X ability" perhaps even annoyed for having to in the first place; but overall it's towards strategizing and preparing yourself for different encounters; and though there might be a learning curve, I'm sure not only we can get used to it, but it might a pleasant surprise & a change for the best! 
Something else to consider: don't think Tactics are tied into this, your Companions & Inquisitor will still use unmapped abilities that you have assigned them to meet whatever conditions. Another plus IMO towards strategizing, in that you can scout/analyze the field, plan ahead some neat stuff out & maybe fill in that which you've "left out", so to speak... O.o?