Because melee DPS has the strongest limit break.

Healer/tank limit breaks don't do damage so they're useless.. BRD has... healer LB who knows why.. then BLM/SMN LB are aoe, thus weaker than yours on the boss.


So yes, if you're finishing off the boss, go ahead and use it, they're not trying to boss you around, there's just no need to use a healer LB on a regular dungeon boss..