Played some more with the Assassin, you do need to commit some points to the melee fitness spec in order to kill mooks through shields with a single hit. Ultimately it's probably not worth it, but you can still punch unshielded troops to death pretty easy. In general, I think 4/6/6/6/4 is the best way to take him, I settled into a good rhythm with the Wraith, cloak->deploy mine->shoot->homing grenade->detonate mine, and permutations thereof. He's basically always putting out damage this way, and assuming incendiary ammo, making explosions all over. Great character, lots of fun.