Lord Kri
Theoretically, the loot gained by this encounter is determined by the order you kill this bug family, although the encounter is currently bugged (no pun intended) and no matter which way you drop them the loot is identical. In order to get the best loot, you need to kill the hardest one, Kri, last. The easiest way to complete this encounter is to kill Lord Kri first, then Princess Yauj and finally Vem. Until Lord Kri dies, have hunters keep Nature Resist up, shamans doing poison cleansing totems, druids curing poison, Paladins cleanse as much as possible whilst priests and druids keep up the heals. Take Princess Yauj far away from the main raid, and start working on Kri. When he dies, a very damaging poison cloud will appear, so make sure everyone gets far. After him, kill Princess Yauj and make sure casters are ready to kill all the litte bugs that will spawn, the princess also heals so ensure that you have a number of rogues to kick her when she casts or mages to counterspell (she is immune to the silence effect and can resist easily), Taking into account the AoE fear this can be rather tricky so good tactics are needed. Horde can also use Tremor totems to great effect in this fight somewhat simplifying it. After she dies, just finish off Vem.
Fear Ward is a MUST.
Princess Yauj
Princess Yauj is an optional boss in Ahn'Qiraj, who comes with 2 other bosses: Kri and Vem. Yauj has a range AOE fear that wipes aggro even if mitigated with Fear Ward. This fear will make you go out the door and can have the 3 of them reset, Therefore, strategy to beat Yauj is to tank her as far as you can from the main raid. Also, when you have started to kill her, she will cast a self-heal, which needs to be interrupted.
When Yauj dies, several small bugs spawn. For complete strategies, read the Lord Kri entry.
Vem
Vem is an optional boss in Ahn'Qiraj, who comes with 2 other bosses: Kri and Princess Yauj. Vem has a charge ability.