Honestly Cover and Shield bash are both less useful I'd get rid of both way before clemency.

Clemency is
1. A good emergency tool that is actually consistent unlike cover.
2. Good Solo tool, blah blah "omg shield bash is like useful at stunning a mob"
3. A good progression tool, if you're learning a fight it's actually one of the best consistent skills at seeing fights longer and learning more.

Ideally clemency would be a OGCD MP tied ability leaving it so that if you spam it, by proxy you still lose damage because you have magic tied to damage, but good useage of it will lead to no such loss, maybe just remove healing on spell attacks though if this was ever a thing.