Heart of Life (and, I assume, any other thing with interrupt upon damage) is interrupted by heals from allied priests. I've died once or twice because of this. Apparently it's an old bug that got forgotten.
This issue is based on the fact that heal spells at this time only do negativ dmg, eg. if you get healed by 500 it is actually -500 damage. Ever wondered why your demigod spams the "i got hit" sound if you regenerate at a health cristal?
Any damage taken will interrupt things like Heart of Life, so even "friendly" damage like UCBs Ooze ablility. To fix the problem with heal interrupting, the devs can't just take away the interrupt if you take firendly dmg. Or they would give UCB the ability to heal with HoT even with activated Ooze. Because it looks like the devs have to change the whole healing system you should prepare youself for a bit longer waiting time. 