This is not so much of an exploit, it is more a very clever use of mechanics.
In our attempts to clear Steelbreaker last we found that the healer was put under a lot of pressure from dispels.
Basically we had myself the lock use a felhunter with shadowbite turned off (it uses a gcd)
I played desto but any other spec that doesnt use a felguard is more than viable.
Now bind /cast [target=focus] Devour Magic to you main spells, in my case i bound it to Conflag, Incin, Immo, Chaosbolt.
Set Steelbreaker's tank to your focus. there are other methods of setting this macro up, focus is convenient since when you change tanks you can change focus.
When engaging have your felhunter sit on Steelbreaker, set the tank to focus and mash your keys.
Basically when steelbreaker casts fusion punch it will not hit the tank at all as it is dispelled instantly.
At the end of the fight recount looked something along the lines of:
Pet Name (Lock Name): 14
HPally: 3
RPally: 2
The DPS loss from not using an imp is not a huge amount but we managed to kill steelbreaker with only 1 tank dying.