[DUPLICATE] [Ulduar] They're Coming Out of the Walls (10 player)

[Koler]

WoW Freakz link: https://www.wow-freakz.com/achievements.php?achievement=3014&&name=they-re-coming-out-of-the-walls-10-player
Bug description: The counter is bugged, you don't get all the mobs counted in the achievment. The maximum you can get is 6 and sometimes you even get 0, even if in the screenshot it can clearly be seen that there are more than 9 dead guardians. I even killed 30 and got only 1 counted.
Proof: http://imgur.com/a/6dPc0
I'm also opened to suggestions on how to do it, I tried it for 4-5 hours to get it and i think the mobs which have the debuff or those which got they're HP under 50% from Sara's Anger don't count towards the achievment.