Bacon Bits
Legend
It's powerful in my IWD game, that's for sure. It's also kind of tedious to run - the player having to constantly update people on how many bonus HP they have now, and the fact that it triggers at the end of each player's turn keeps confusing people. We also had to work out that it doesn't save someone who's bleeding out already.
I would pretty quickly change it to work at the end of each of the cleric's turns and off a single die roll. No, it's not identical, but it's also not really worth the practical difference in the effect in exchange for the increased overhead.
The bleeding out rule is in the PHB. Not sure if that's what you meant. You can see it in the Basic Rules under Combat > Damage & Healing > Temporary Hit points:
If you have 0 hit points, receiving temporary hit points doesn't restore you to consciousness or stabilize you. They can still absorb damage directed at you while you're in that state, but only true healing can save you.