As has already been said, I think it'll be 15-20 seconds and a case of switching between either Storm's Path or Storm's Eye debuff for tanking situations, then applying both when not needing the enmity; (either far ahead on enmity or not wanting attention on you).

Presuming that the changes to enmity in 2.1 aren't so absurd that you can keep hate with only 1 out of 3 rotations being BB of course.