Fortnately I have 5x paladins so bladestorm doesn't do too much damage. But that said i still will switch to the warrior and burst his ass down.

On my shamans the best thing I can tell you is to simply have a spread out macro and spread the hell out then start healing whichever shaman he is sticking with, after he is done FS+LB that A-hole into oblivion. Actually come to think about it,this is what I do for all melee that are exceptional pains in the butt and when TS is on CD.

Edit: For Rogue's FoK on my shaman team I always have poison cleansing totem on my pvp totem sequence so that takes care of that.