You’re not the first to notice this. I posted here about the same topic , and it was previously posted about in a broader sense here .
It’s a very silly design choice, but beware that some people will argue that Zealot is meant to be played at HALF health with only some of his buffs active, and until death and the most powerful versions of his buffs are merely emergency stopgaps at low health until you can heal. I think that’s objectively less fun and probably wrong, but they will argue that.