I have Despair at Mastery level three; which should reduce healing by 15% per debuff. Usually this seems to work; but it doesn't against Mephisto:

As you can see, I have nine shock charges on Mephisto, but he's still healing significantly.
I suspect this is caused by a flaw in the coding that makes Mephisto invulnerable whilst regenerating; as there are other instances of him healing when he shouldn't:
https://forums.playcontestofchampions.com/en/discussion/60141/is-mephisto-broken#latest
Could a Mod please arrange for this to be looked into?
Thanks.