That's right. Add in a Brass arachnid for some real schenanigans. get a reactivate off on the swarm, and it can activate using all it's actions, enemy takes a turn, it goes again, using the two melle master attacks, use a general AP to split, then the individual spiders get an AP. Enemy takes a turn, then the individual spiders use the reactivate they inherited and go again.
Nothing like a minimum of 33 damage should you hit each time and get weak. (that's assuming the spider's weak dmg is 3 like I think it is, can't remember)