I think the various CC abilities and Utility abilities are what set good players apart and decide a class' skill cap.

- Monk: Knowing when you need to use Incap to get off a leg sweep or disable. Knowing when/how to use Healing Sphere. Using FoF as a damage ability vs a control ability (sometimes you need to just get the tick off for a stun).

That's the only example I can think of atm.