Well, it's really different if you play on Nightmare, because then your mages will kill your own partynyysjan said:Only reason i did not have a group of nothing but mages in DA:O was because there was not enough mages (holy fuck those guys were OP), could not force myself to play 3rd act of DA2, but they really nerfed mages in that game.
You should try a dual dagger rogue backed up by double haste (which you indeed need mages for), momentum + swift salve. Rapes everything a new one, even burns through high dragons and everything in seconds.
+ You can make warrior tanks virtually invincible (also to magic).