Kiting the adds is iffy. (it can work..sometimes) The instant ability the adds use is called Scourge of Nym. and ive seen it hit me (the tank) for anywhere from 300 to 4.5k dmg. the upper limit just sees rare, but i have no idea why it has such a large gap in dmg.

the strat i've used for winning is basically the same as everyone else's though, Tank tanks boss, 1 DD on boss, 1 DD on adds. and everyone rushes boss once slashes appear.

also, 5 is the cap on Stacks of rancor :x. had a BLM LB king and the adds and he only gained 5 from it, even though there where alot more present.