Besides the already difficult to discern determination between an unblockable attack and one that seems unblockable but isn't really (which is super, super frustrating - if an attack is yellow, why is it unblockable? Red ones are, not yellow, and yet, with eorforwine, there are unblockable yellow attacks?), the difficulty involved with taking out these self-healing health sponges only encourages cheesing them (staying at range, spamming spear return, etc).
Odyssey had some of the more fun boss fights of the entire series, to be honest - all the world bosses, while taking a decent amount of time, had a rhythm you could get used to and start working around. There's no such thing like that with the zealots - only spam and cheese. Really feel like they should be rebalanced.