I set Sten up as a Berserker and he did fine by me. As mentioned, not a great tank (Alistair seems best for that) but does good damage.
You can actually thread the needle and kill off the Circle without losing Wynne. Don't ask me for the exact path to take in the dialogue tree but I did it last game without intending to. I was actually surprised to find that I had inadvertently killed them all since I had planned to save them to avoid angering Wynne. Of course, if you continue to act like a **** I'm pretty sure she leaves anyway (i.e. if you defile the Urn).
Edited, Apr 24th 2012 6:01pm by Jophiel
I think I do remember thinking about that, actually, thinking about it. Just looked it up on the wiki:
1. Recruit her after you defile the urn. Doesn't seem like you can reason with her about this, even if she's not in the party.
2. You let Uldred kill Irving, but don't openly agree to Annul the circle when Cullen asks. Whether or not you actually try to save them doesn't matter, as long as you promise to. So the circle gets destroyed, but Wynne stays with you. Without Irving, you get Templar support.
I haven't actually Annulled the Circle, so no clue what happens to the other mages. I really need to get around to trying that out...