Bladestorm's saving grace is that its contribution to boss DPS is nominal, and you only have to use it once every two minutes.

I've spent the majority of my time on the beta testing Arms and providing feedback on the forums, and am confident that Arms will remain competitive throughout the next expansion.

The first significant change is to Heroic Strike, which currently provides as much as 30% of a Fury warrior's single-target damage. It's now on a three-second cooldown and its cost has been doubled. The second change is to rage. In Wrath, gear (and the Heroic Strike bug) has allowed Fury warriors to generate nearly unlimited resources. Blizzard is still refining its solution, but rage is intended to scale subtly with each tier, preventing the same leap in output and requiring players to make choices about how to spend their rage.

There are still some concerns with rage generation and Slam, but with this balance in place, the devs should be able to structure damage to make (and keep) Arms viable in a raid.