Well normally people split on Shamans on HC
Nazgrim, how often is the adds stacked up?...
Malkorok, just DR and keep your normal rotation up, no need to use a Bladestorm for 1 target.
Thok, so now you are talking about thrash?.. Otherwise it's a straight up singletarget fight again.
Ranged should do the mines, you should be doing either assembly or 24/7 boss.
Klaxxy, well it's cheesy to use bladestorm on Klaxxi, might as well just use Dragonroar for it.
Garrosh is a fight where Bladestorm us usable several places, not just adds, but also MC and desecrated weapons
I really don't see why you would use Bladestorm on any fight where it's a straight up single target fight. You would need at least more then 3 target through out most of the fight for it to be an increase compared to Dragonroar.