How to make enmity combos relevant:
- Rework enmity as a system.
- Mostly remove the enmity component of enmity combos, siphoning the bonus towards some new system.

Or:
- Effectively trim Shirk.
- Diminish other enmity-circumvention skills somewhat. This may even have to include Cover's SB trait, which effectively applies the same between tanks in circumventing a tank swap through optimal play.
- Slightly reduce the relative potency cost of Butcher's Block (and likely other enmity combos) and the delay of enmity application in enmity combos, perhaps in exchange for some of the actual enmity produced.

So long as it's a quickly capped table, there's no reason to use enmity skills beyond opening burst and particularly frequent obligatory tank swaps. It serves its purpose, but, yes, that means it's about as single-use as a Bard's Caustic and Storm in any continuous fight.