They need to add a button that sais : Simplify Rotation.
That button, once toggled, removes all buttons from your bar, and “fades them out” in the spell book. All except the 3 or 4 core skills that define your class and spec.
And the talent tree would be fixed and not able to be changed. It would be all passives. Even if you have to skip active abilities to get to them.
All modifiers will not be shown at all in the screen either. All the stuff next to your toon party frames.
DONE.
That is what they need to do.
Egs: You play a Arms Warrior.
All the buttons they have become: 1) Charge. 2) Mortal Strike. 3) Overpower. 4) Slam.
Egs: You play elemental shaman.
All the buttons become: 1) Wolf 2) Lightning bolt 3) Chain Lightning 4) Earth Shock
DONE.