Well, Blade Flurry causes rogues to get aggro on side mobs anyway. I'm already trying to keep aggro on the skull, I can't afford to do the same for a second one on which the rogue does identical damage for 10 seconds straight. I had this guy once who would use Blade Flurry on cooldown in a Hc SV or SHH, can't remember exactly, but he wasn't using Evasion with it (it has the same cooldown, why not?) and was pretty much dying all the time. I mean, yeah, BF does superb damage and definitely makes Combat outshine the two other specs in HCs, but if you're not gonna combine it with Evasion and just die, then what's the use? And after the BF + Evasion combo is over, just Vanish (which also has the same cooldown) and re-open. Easy.
It's not like it's hard to just sidestep a bit so your Blade Flurry can cleave to another target in order to avoid aggro. But eh, I guess I'm getting elitist now, having played these 2 classes for 80% of my time.