Never played Bonus Mission Pack, though. I have a problem with them too, in a coordinated team though, where this is discussed and agreed upon in advance, skills like these could prove very useful.
Imagine a mob vs 3 players, of which 1 necro with Sacrifice Other and Arcane Echo. I'd be an instantkill (well hopefully, because the Necro would probably run out of energy otherwise) of the whole mob. A bit like those self-sacrificers in JQ.