To continue with the above: notice that checking wsrep_local_state really doesn't help since it is equally broken. It is possible that a node is in DONOR state yet it is fully in sync because SST method is xtrabackup or it is donor to an IST operation. So is you conclude that a node is not healthy because wsrep_local_state=DONOR then you will get a lot of false positives.
To continue with the above: notice that checking wsrep_local_state really doesn't help since it is equally broken. It is possible that a node is in DONOR state yet it is fully in sync because SST method is xtrabackup or it is donor to an IST operation. So is you conclude that a node is not healthy because wsrep_local_ state=DONOR then you will get a lot of false positives.