I personally avoid using clemency where possible, unless healer is really struggling with a big pull and I miss time a CD, and like ~15% hp and healer is spamming heals, or it's prog and healers are down, there is genuinely no other reason to use clemency and hp penalty on spirits within (stipulation does not belong on a tank), isn't really a reason.
Personally it feels disingenuous to the healers, who are there to heal and in harder content it can screw with their planned healing. Remember if you do die it's just a game go back to the start or get a raise, just let the healers to their thing and worry about doing dmg, longer you waste using clemency the more damage you take overall because you're not doing damage.