What good is a vamp horror?

What good is it? better minion wall than bone???

The Minion skill is good for keeping your casters protected. Due to their low level--and the low AL that comes with it--foes will generally target them first thing instead of the casters in your team.

Vamp Horrors aren't really great on their own. They're nice, but they could be better. Consider using Order of Undeath with a bunch of Vamp Horrors. It'll increase their damage, and that will increase the health you gain, making up for the sacrifice. It takes a while to get going, but once it's rolling, it's very effective.

It gives you health, can prove usefull if you are running [aura of the lich] or [order of undeath] bar. In first case you have more "tanking" ability and in the second you are less likely to kill yourself with the order.

Generally there is little need in vamp horror unless ou are running the above bars, in all the other cases [animate shambling horror] is much better.

For OoU, yes.
Accompanied by Fiends for it's cooldown.

If I was running a hero, Bone Minions. Soft targets which have 2 and can be 2 easy bombs.

would vamp horrors + bone minions + AotL be good? I only have Proph, Factions, and EoTN. I'm trying to do the In Defense of the Eye quest and i'm thinking of vamp horrors so i can get healed. or am i better with bone fiends/bone horrors? should i add mark of pain to these builds?

actually if your bar permits I'd take all 3 types, vamp horrors are great for the aforementioned healing, and fiends are great with their increased attack rate and range, however vamp's recharge can prove prohibitive and the 25e for the fiends can also prove prohibitive. Good old vanilla bone horrors can fill the gap between the two, they're great cannon fodder to use in fights where you're low on energy and can't wait for vampiric to recharge.

of course I typically use OoU so perhaps with AotL the energy issues (not always having 25e for a new fiend) i sometimes encounter wouldn't be an issue.

Use them to cover OoU sacrificing if you're parting a with a monk who's less competent than Mhenlo - otherwise there's no reason to use them.