Oh man, imagine the QQ of people an arena team that gets their members sequentially offed by a ninja-assassin squad. First guy, probably the healer, gets 5 knifes in the back, Vanish, sprint off, get behind and ambush anyone trying to rez. Blow preparation, vanish again. You're now up 5 to 2-3. Wait on shadowstep, shank another guy. Brute Force your way over the last guy or two.

Sounds great until they all put their back to the wall or something.