The thing is, on paper, MM has the right tools to enable it to be an excellent kiter: its range is longer than the 40 yard max every other spec gets, its slow can be refreshed on CD or by steady shot, it has a disorient, a (skill shot) knockback, an AOE slow, a freeze trap, a ranged interrupt, can break cast times with FD, get away with posthaste, and can have a pet with its own slow…and we’re not even getting into its offensive abilities.
A better question would be, with all of these tools, why can’t it kite indefinitely?