[Snake]

Well, Desperado has it's own appeal, which is Bullet Barrier. Reaver doesn't have anything worth to make you want to stick to it, so I don't think it would be necessary to punish people if they end up misusing a stance, for example, when you're in the middle of a Reaver Combo, then notice you won't have enough Momentum to swap back to your defensive stance, be it Desperado, Cobra or Matador.

And the idea for the statistic buffs while you're in a stance is just to make them 'feel' more powerful for a stance, you know. You swap to a stance and then that's it, it's not making you better, just allowing you to do stuff and not do other stuff. And that's too bland for a charming class such as Demon Hunter.