My comment about Haunt is the top rated one on wowhead (Oronare) and there are a few things about Haunt;
1. If the pet dies whilst you are Haunting them, your pet will also die
2. Whilst "dead" your pet does count as a corpse for the purposes of consume corpse, you aren't consumed either, eventually you will pop back out alive and well.
3. If Haunt is dodged, blocked or deflected in any way, your pet just dies.
Everyone I've ever seen in PVP with this pet takes Unholy ascension, for obvious reasons, if you pair Haunt with Curse of Doom you risk killing your pet when CoD explodes. I've never liked the pet to be honest, the model is fantastic and fun, but the pet for pvp is pretty bad, if you are going to take an Undead Curse pet, take the Crawling Claw or something, it has a lot more utility.
if you're winning 80% of your pvp battles using the Val, then you must be playing some pretty terrible people, any team with a s/s rabbit on it just annihilates it, even some Humanoids like the idol and Flayer can kill it off (although usually dying in the process because of the Undead rez. Deflect the doom explosion, kick, sandstorm to reduce damage etc)
So that is how haunt works =) I'd choose another Undead if I were you. Bone spider, Claw, Skull, Blighthawk or something like that. =)