I agree with eggspr. If you're running a knight bus or CH (or something that is equally expensive and can be healed easily), a level 4 vampire caster ist a must have. Those knights are very hard to kill and to get back 5 of them in each of your magic phases is simply awesome. The most players know this and will try to dispell your IoN. They are, simply spoken, scared that their precious kills are undone. If your victory doesn't depend on this one IoN you can be fine with this because it often leaves you with enough PD to get one or two other spells (hopefully more/equally important) through. I know this tactic of casting your spells is as old as magic itself but IoN is that cheap but can be that fearsome to some players that it works better than most other spells.
I like death magic. I've used it a couple of times, mostly on a level 4 MN (supporting my ghoul king) and I can see the benefits of having a death casting vampire in the general's unit. But then you have got a death star of some kind and I don't like the concept of a death star. If it hits, everything will be smashed to dust but if not (and many many players know how to avoid it) or if it is debuffed/shot at/feed chaff heavily, its main purpose is lost. That's why I use a shadow vampire in a ghoul horde. The sig-spell has a range of 48'' and therefore can support my knight bus even from afar and the vampire himself upgrades the ghouls to a considerably fighting force.
@eggspr: Do you think a level 2 death and a level 2 shadow could work? I would put the death in the general's unit (maybe even replacing the wight king) and leave the shadow with the ghouls. But then again, you won't probably have enough PD to cast with both lores and the chance that you get the favoured spells is small. I was considering taking another shadow vamp. The chances of getting doubles are much bigger and choosing your spell(s) is never bad. Even if the list is not designed for mindrazor (and I think I wouldn't take the spell at all), two shadow casters could be very good. But maybe it's just me loving the debuffs of this lore too much.