Or freezing trap one, sheep the other (NOTE: sheep is non-directional...you can cast it while facing the other direction ), continue focusing on Wyrmthalak until he's dead. Then worry about the one that's coming out of the freeze trap (resheep the other one). Kinda depends on how your DPS is doing at that point. Conserve mana until then so you can DPS dump on the boss while the other two are CC'd.

Can't say how it'll exactly work for you as I did this at 60 with the priest and 4 demonology locks. My DPS was such that Wyrmthalak keeled over dead about time the 2 adds were halfway up the hall.