Hello Everyone !
You will require to be either a Night Elf(Shadowmeld), Rogue(Vanish) or Hunter(Feign Death). I found this exploit earlier today while I went in there to farm the 4 mounts for credit towards the following 2 achievements:
Why? Because It's Red
Mountain o' Mounts
Basically as you enter the Temple of Ahn'Qiraj raid, There are 2 types of mobs you come across before the first boss. They are 1x 'Obsidian Eradicator' & 4x 'Anubisath Sentinel'. You can kill the 1 Eradicator but the exploit is to not kill all four of the Anubisath Sentinels , Kill 3 of the 4 & Simply Feign Death, Shadowmeld or Vanish right after the 3rd dies and all four will respawn instantly. Rise and repeat.
This will allow you to consistently farm the mobs till they drop the mount without having to go out and reset and most importantly avoid the 5 Instances per hour limit. I haven't contributed in a while and I hope some of y'all find this useful.
Enjoy !