Alright - PoP has been out alongtime - Time to start posting some REAL info on these mobs...
Vallon Zek is kinda a tricky encounter. You start with JUST one. When he gets to aprroximatly 30 precent life he splits into 5 more (all with full life.) Of these "new" Vallons one is real. When that one gets to 30 percent life - he splts again. Anyrate, this goes on through 5 splits. Obviously the trick is to Identify the "real" Vallon Zak and not kill him til after you have killed the fake ones, or you end up with a TON of hard hitting level 70 mobs REAL quick.
Vallon Zek melees in the 200-800 range - i have seen double and triples no quads. He hits prety slow to begin with and IS slowable. Hes a NASTY NASTY AoE curse/DoT (cureable by radient cure 1.) Its soemthing in the order of 2k damge in 30 seconds or so. I've NOT parsed the DoT thats just a guess, but its NASTY.
This encounter is COMPLETLY trivial once you know how to do it. (Trivial as comparred to what you would expect in a tier 2 zone.) For example, any force capable of killing Xanamech, should be able to do this guy, ONCE you know the strat.
Theres your info, if noone has posted a strat I might ina few weeks.