Huh, weird. Did you keep Threaten up? That made a big difference for me. I also had him go champion and use Warcry whenever we were surrounded. That helped too for some quick snap-to threat on multiples.

For my arcane warriors, I don't even bother with a dedicated tank. With all the defense toggles up, I'm nigh invincible... of course, with so much mana tied up in those toggles, I cast a lot less spells, so it can be kind of boring just whacking away with my sword while I wait for regen sometimes. :)

Ugh, Wynne. I'm always tempted to side with the Templars just so I don't have to take her with me through the Tower.