I don't know if it's just luck, but I'm really not finding much difficulty using m&k controls, especially after tweaking some of the keybinds. My biggest complaint is that I need to use both hands to move my character around (keyboard to move character and mouse to move camera). It would also be nice if they included an option to area-loot or select to loot from a distance, but honestly, this wasn't something that started bugging me until after I heard people complain about it.
As for respawns, MINOR SPOILER:
I did get frustrated with this in the Hinterlands, when I practically had mage and templar fights spawning on top of me - while I was still in the process of trying to loot the mages and templars I had just killed. However, once I discovered that you can eliminate them from the area by knocking out their respective strongholds, I went on a bit of a crusade and haven't been bothered since. Did the same thing for the wolves, now it's just the occasional outlaw or sellsword I have to deal with, and I'm finding exploration through the Hinterlands to be much more easy going.
Overall, I'm enjoying the game quite well, though I'm still quite early in the story. I'm finding myself liking some of the characters a lot more than I thought I would. Also, I have played a LOT of MMOs, so I'm not as bothered by the gather and fetch quests as I can understand some would be.