I don't play as frequently as some, so maybe I haven't noticed...but is there an aggro system in place? I mean, how do the monsters decide who to attack? Is it whoever has dealt the most damage to them thus far?

Many times, it looks like the monsters just go for whoever hit them first. Then my warrior comes up and starts wailing away to get them to back off the archer or enchanter who's running away with a tiny life bar...and no matter how hard I hit they ignore me and keep chasing my teammate!

Maybe I'm just misjudging how much relative damage I'm doing. But if there really isn't an aggro system, I strongly recommend it. Aggro would make being a tank a bit easier when you're playing with trigger-fingered ranged players who won't wait for you to go up and whack the baddie first. Yet, as tanks usually don't put out the most damage battles would still be dynamic (enemies changing targets).

Sorry if there is aggro and I just didn't notice.