There's a difference between requiring skilled usage and being straight up bad.
Inner Beast requires skilled usage because it is on the GCD and needs 5 wrath stacks that you could be spending on Fell Cleaves. There is minor decision making and strategizing involved in using Inner Beast.
Your suggested change is straight up bad. It functions just like the current ability, except worse.
It decreases the net benefit from the skill (CDs that cost hp... what they are intended to fucking protect) and requires more work from the healer for tank busters.
Sure, a skilled team can make your suggested change work... but that doesn't mean your suggested change is not a nerf disguised as a "design" change.