Well, you aren't factoring in the rate of spawn. They gave these buggers the old Fel Ruleset of an almost instantaneous Spawn. If it takes you 10 seconds to kill, with a 5 second respawn timer, your 10 second Kill is slowing it down considerably. You triple your man power and bring it down in say 2-3 seconds. then you double your Speed.
In all honesty though, the mages will give you just as good of results with less effort/manpower. Toss a thrower in the big room, and a thrower in between the smaller rooms. WHam bam Thank you mam.