1) Not all. Some are fairly niche. Many are though.

2) We have no idea at this time. Though, it's speculated to be likely.

3) DRK, not so much. WAR yes, they have fewer "Niche" skills, only 1 AoE skill and have their Gauge Spenders consolidated into 2 buttons (For 4 skills. Inner Beast and Steel Cyclone in Defiance. Fell Cleave and Decimate in Deliverance) though they're still pretty full on keybinds (I have 3 full action bars even with culling what I can)