Seriously guys, make up your mind...
The game tells me, it is some sort of projectile attack, judging from the "Number of Projectiles: 1" line in the skill description(hopefully a bug), since it does not benefit from projectile damage increases at all! But it is also a melee skill, which does not actually "hit" enemies, it does deal damage, yes, but on hit effects, such as the "Flurrying Flames" talent are not triggered.
Overall one of the worst feeling and mechanically functioning skills in the game, but sadly still the go to for clear speed...
Edit: Flurrying Flames can be triggered by Bladestorm, the talent is simply bugged and only works sometimes with Bladestorm it seems.