Methinks you havent looked very well at it, it does have its uses. Fight till you are near death, then pop unholy ascension and finally an empowered curse of doom while the rest of your team benefits from it. And as some have stated, they shine quite well on some beasts of fable.
This is a very good pet for both PvE (against the BoF) and PvP (Haunt opens up a lot of possibilities, and Unholy Ascension is as powerful as ever). The only downside is that it seems to be very hard to collect.
I regularly use this pet with two beasts to take out Nitrun and coupled with two fliers to take out the fishy fable beast. Many people have been using humanoids on their pvp battle teams too. Lots of win.
Well I use unborn against Nitun,Ka'wi, gorespine, greyhoof, skitterer, and lucky yi daily. Sure you can get plus 50% damage from something like flock, but it lasts so short that I find 25% extra damage for pretty much the whole fight really helps.