I normally use provoke initially because there is always at least one or two impatient DPS who throw out a nuke before aggro has been well established. When tanking a single mob that doesn't involve switching between tanks, I shouldn't have to use provoke at all, which is why I dont mind tossing it out initially and waiting for its CD. Also, IIRC Provoke is not on the same GCD as the rest of my abilities. So it generally just buys me a few seconds to get my first RoH combo off without losing aggro immediately.