Initiative is the problem here. The Necrotic could well be dead before the unit he's in gets to strike, wasting the hatred and pts.
MWBD offers some defense in the way of getting hit less via the higher WS of the unit. With access to Van Hels, and the ability to equip the TP/TK defensively, you can really make a tough unit.
This, is of course, very dependent on the unit you wish to buff.