Ok so I just read a thread on the wow forums about some guy who tested it. So I had to try for myself. And what the hell do you know but the backstab glyph...20% more damage while target is stunned...is WORKING WITH MUTILATE!!
heres the proof. First I did 50 mutilates without the backstab glyph:
50 mutilates
80k total damage
Average hit: 993
Average crit: 2381
Then I went to the auction house, and bought the backstab glyph and used it. I used sinister strike to build my combo points, then I kidney shotted the target dummy and mutilated it 2 times each kidney shot. Here are the results.
50 Mutilates
98k total damage
Average hit: 1172
Average crit: 2818
***NOTE*** I am currently not spec'd into improved kidney shot. These numbers are strictly from the backstab glyph. Hope more rogues will test this to prove it is true.
The glyph is getting nerfed next patch but w/e at least we have 20% while stunned until then
