http://www.project1999.org/forums/sh...ad.php?t=39361
This wasn't the discussion I remember from a few months ago, though.
Ah ha! Found it, just had to look through my post history for a few minutes. Rogean says aggro is based on damage potential (well actually he says on "swings," but whatever)
http://www.project1999.org/forums/sh...722#post586722