Meteo and Warriorsarri already covered it but...
Norushen - Of course you want to Bladestorm the adds; they need to die and they're an important mechanic of the encounter. BS is ideal for them unless your guild uses a strat where the adds are never clumped. Chances are though, BS is still probably better since you're very likely going to have enough adds in range to make BS preferable.
Shaman - They typically don't split them until the dogs are dead (or near to) and a Reckstorm at the start with all cd's and procs lined up is pretty huge. For any single-target portion of the fight Bladestorm is still acceptable. Dragon Roar is absolutely a big contender on this fight, no denying, and anyone progressing on the boss will probably be better served with DR.
Nazgrim - Entirely depends on strategy of course. If the adds are never anywhere together you'll certainly get more out of DR. For those who do get adds in proximity to each other, BS is just as good. The pudding goes to those who get to Reck-storm on the pull with all the initial adds up
Malkorok - BS lines up almost perfectly (assuming Evil Eye) with every other set of adds. If you're using a strat where they're not pulled to melee, or where they die before they get there of course DR will be better. Most strats I've seen however typically try to get the adds to the boss so they're not creating difficult or impossible situations for the ranged.
Thok - I'm absolutely talking about the bats, which are a very significant mechanic on Heroic. Significant enough that they pretty much *have* to die ASAP and it's enough to warrant using BS for. Also, as Warriorsarri noted - BS has a slightly larger radius allowing you to potentially keep tagging Thok while he's running by.
Siegcrafter - As I originally stated; DR is, at least in my case, the default choice since I'm on conveyor duty. I already covered this...
Paragons - It's not cheese at all. If you don't understand the diminishing returns on DR, then one might consider it as cheese. If your guild uses a strat (that I have yet to see) where DR's won't clip multiple targets, then by all means, use DR.
Garrosh - Already covered really...BS is a big deal for every phase other than P4. Just be sure you're not abusing BS damage in P1 in lieu of pushing Garrosh (this holds equally true for *EVERYONE* aoeing in P1, not just Warriors). BS on adds in P1, Embodied Fear and Doubt in the intermissions and on MC'd people.