Having looked around the bug report forums, wowhead, etc., I haven’t found any topic about this particular issue yet.
I believe there is an edge case involving the Nigh-Invulnerability belt and Cheat Death that needs to be addressed; at least according to the wording of the Cheat Death tooltip.
Cheat Death says:
You have a 100% chance that an attack which would otherwise kill you will instead reduce you to 10% of your maximum health. […]
However, in a recent arena match I popped Nigh-Invulnerability while very close to death (632 health) and while the Nigh-Invulnerability buff was active I took a hit for 662 damage and that caused Cheat Death to proc given I was at 632 health.
From my understanding this is not the intention of Cheat Death. With Nigh-Invulnerability active the 662 swing was not going to kill me, it would just have taken 662 points away from the shield. Effectively, with the buff I have 4632 health as opposed to the value 632 that the game validated against.
Here are the screenshots of Details relevant to this bug:
https://i.imgur.com/osAKInS.png
I included the death log which (highlighted in yellow) shows the important sequence of events. I also showed my buff uptime and debuff uptime to prove the belt didn’t backfire and I did in fact have Nigh-Invulnerability active.
I recorded the video of the match as well which shows everything I’ve previously stated. If this is required for verification or additional information of the suspected bug then please let me know and I’ll upload it so it can be analyzed.
Edit: Nigh-Invulnerability was not spell stolen either, it was active at the time Cheat Death proc’d and for multiple seconds after that.