[Wendigo]

Of course a pretender is a valuable target, but what's your chance of randomly targetting him on your 1st attack among the 30 or so commanders in his army? And once you have shown your cards your opponent will be ready for further attempts: expect scout chaff, heavy patrolling & assorted traps for your assasin.

Personally, I find a barrage of assasinating spells much more cost-effective & flexible than knife-in-the-back assasination, at least in MP.