You do have to kill them all, it was just an easy way because if you went up something with steps, the NPC's came in one at a time and when there were 6 of you standing there with pointy objects, you made rather quick work of the wave, even if it was a difficult one.
Would be an idea if it were an openish field, save for maybe some fences or something to duck behind out of crossbow fire and then have the player be the VIP and do something like CS did and standardise their armour, health, movement and weapon so that it doesn't randomly give a new player that dies in 1 hit VIP or the player you're crutching on.
Few ideas for it anyways, probably should throw these in the suggestions forum since DTV is fun when you want a while of mindless bot killing.