I see a lot of problems with the idea of Roll the Bones being RNG. Though I haven't been able to play it in Alpha, I can very much understand the frustration that it'd bring in a raid setting. Slice and Dice has been fantastic as it's simple, consistent, and has no luck involved in the application.
Personally, I'd revert back in keeping Slice and Dice baseline and Roll the Bones to a level 100 talent slot with a very specific change in design.
Within the Roll the Bones talent which replaces Slice and Dice, have the random combat enhancement built on-top of Slice's attack speed boost while tuning appropriately. This will keep the original consistent intention of the CP spender, while adding the bonus RNG element of Roll the Bones.