I noticed that certain people will only attack enemies that are already engaged, especially if you are alone.
I usually go THF and have noticed that it's possible to Hide from the enemies in order to
shed aggro. You can use this for frontal WS with SA stacked (Especially if a Quadav puts on Diamonshell, all hits from the rear are 0 DMG) or you can use it to break yourself away from NMs to find a Pixie/Sprite.
Hide hate breaker
If you want to be a dick...
This works really well if you fight on top of someone that just died. When the person accepts a raise hit your Hide macro. It's wonderful fun and I can't stop laughing when it's that melee mage that wasn't raising anyone, lol.
You can also force that melee mage to tank as you walk away.