Or the servitors put a shield around all the enemies making them immune to attacks until the servitor is dead. Imagine two or three sepkis prime type servitors with a shit load of snipers behind them and dregs chasing you. Also, for wipe, they are military based so who says they don't have like an atomic bomb or giant Ray that will kill everyone if you don't beat something in time. Or a large ketch that just bombards the battlefield until everyone dies