For rogues, this should actually be pretty easy. Just sap everyone that's in your way, (if you have the improved sap in Subtlety it's easier) until you get to where Greyshield is. Sap Greyshield. If you're a subtlety rogue you probably want to go with ambush. Combat might want to go with garrote. Just fight it out then. I have improved ambush, so I crit a 600 and he was immediately to half health, easy after that. Hope this helps!