That is probably the bug, yes. I think that is known, but I don't know the priority for fixing that specific issue.
Yeah, I've been working with our QA to verify issues relating to Permadeath this week, and despite it stopping Ghost/stopping skills that revive already dead targets, there is a bug with the Perfect Immortality/regular Immortality positive effects working against attacks that are trying to apply both Permadeath and lethal damage at the same time.
We're unlikely to have a fix for the next update, but it's something I'm making sure is tracked to be prioritized for a future one.
Sentinel Mayan Priestess taking all is the known bug, as previously discussed.
Warrior Undead Rescuer is supposed to have a chance to take all positives from a single target 75% of the time (when fully skilled), so that is also expected.