i think heavy should be removed. There is no legitimate reason that every single mob should have the same ability. Or at least make it if your 30 ilvls above the mob, it wont agro.

Seriously, what are these mobs thinking?
"Oh there is some uber BLM running through my land that can 1 shot me... Oh i know! Let me piss it off!"

Also if it must be there, then it should have the same limits as our abilities. Get hit the first time for 20seconds, then the second for 10, etc. or at least doesnt reset itself.
Nothing more annoying then heavy effect duration: 3..2..thwack..19....