Something to keep in mind...by the time you're really going to have to worry about losing aggro to a mage you're at the point there that weight is off your shoulders. It's no longer something YOU can control once they have a Relic+1 unless they cooperate and strictly focus on one target. Thankfully, unless you run into a complete idiot, they're not going to complain about pulling aggro on trash mobs since they're more than likely geared enough to take a hit or three without any issue.

This is speaking in terms of farming runs such as AK. I've yet to have an issue with a DPS pulling aggro in an instance like Coil unless it's been a total screw up and something has gone horribly wrong.