Reporting for another:

At level 50, abilities have a flat 75% damage reduction on Prime. However, the Sentinel ability "Wrathful Exuberance" is not receiving this damage reduction, resulting in a significantly large amount of damage because of Sentinel's healing output potential. I do not know if overhealing will still cause this, but it stands to reason that it might do so.

Expected:
"Wrathful Exuberance" damage procs are reduced by 75% at level 50 on Prime

Actual:
"Wrathful Exuberance" damage procs are NOT reduced by 75% at level 50 on Prime