I just think without there being a clear way to stop them or beat them, it gets kinda out of whack. Like the Kenseijin class I made has tons of extra health to the point of at 20th level having well over a thousand heath easily, but a vorpal blade or death effect can off them immediately. Likewise with their being stuck to using a single weapon type, they're very easy to outmaneuver and cheap shot to death which was an intentional flaw with the class to allow a fighter, mage or any other standard class to theoretically beat them.
I'd just say walk back the immunity to death effects, give them a resistance to the effects, or immune specific types of effects. The main way I see someone beating this class is just to blind them and run and let them just die, which I suppose is a fair tactic, but still, just seems pretty unclear. Idk.