1)Huge aggro range. Basically touch the lava pool surrounding the Gatekeeper and the boys and you are going to get all of the guardians. 2) They hit for 500 max. 3) Unslowable. 4) According to other posts, unmezzable and unsnareable too.
They also summon, and when killed Culthor becomes super powered. Currently wiped on him once, trying to figure out a way around his guards or a good kite area.