^^^^ Being disarmed makes you just as useless regardless if you are using bladestorm or not. Atleast while under the effects of bladestorm, it will give you some time to get the hell out of there.
I was under the belief that Bladestorm was never nerfed. It does the same damage as it did prepatch(abid ArP), but with the whirlwind cap removed. A better way to describe the situation is that the spell fell behind when our other attacks were buffed and tweaked, then add the larger health pools of players. Hopefully the 150% WD buff makes it through.