Heart of flame triggers on reserved life

You are not technically "missing" life. If it is supposed to trigger unless you are specifically at 100/100 health, then maybe it needs to be reworded to "not at full life" compatible with 90% mastery, or just change the mechanic to "when you are hit" which technically is already how its working if you don't reserve life. Since currently its completely useless when reserving life or petrified blood, something it would be perfect for.