Summon 5 friends and you're only facing 20% of incoming damage. That's huge.
My last summoner character was spectacular; but fell in the Labyrinth. Burning floor, and Spinning spikes and lag are a potent combination.
I had a great setup going on. Raise Spectre Phantasm on Kill, with Infernal Legion support and the Minion Instability node.
Killing somebody summons a Spectre which does burning damage for 5 or 6 seconds, then explodes. Bedlam :)