Similar event happened yesterday when the servitor spawned for our team off randoms. The other team didn't bother to summon a prime evil. They instead chose to invade us as often as possible killing as many of us as possible each time with supers & sleepers. The servitor kept healing due to our deaths at each invasion. And, though we finally beat it with mere seconds to spare it was a total dick move on their part as far as I'm concerned considering how rare the spawn seems to be.