I don't mind the Tower of Magi, though the Fade part is annoying (which is why I got a mod that allows me to skip it
). I'd say the Deep Roads is my least favourite "dungeon" in the game. Slogging through waves of identical darkspawn (and spiders!) and it's just so **** LONG. On my last playthrough, I had a character with maxed out stealth so I could just sneak past them and skip most of the fighting.