I think mage is the most boring class in the game. Cast times, stationary stuff, can only deal damage... Basically: It's slow. Slow, slow, slow. Everything about it feels slow to me. Yay, you get big numbers, but it still feels slow.
Rogue is a second. I just don't feel like I'm doing anything when playing a rogue. Every attack 'feels' the same, and the combo-point mechanic is inefficient, and overall just very bad. There are tons of reasons not to put something like this in a game, and Blizzard has come up with several things that make the system less bad (like switching combo points to a different target, or generating faster combo points) but the fact that this resource system is so bad at its core that it requires such artifact band-aids in order to be more viable already proves that it is a really bad system.
Basically: Monk chi points are everything that rogue combo points should have been, and I was rather annoyed with the fact that they gave the largest rogue fix to monks. :P