Similar need here for a 3-node cluster — built pihole-fleet-manager to work around it: it stages gravity (blocklist) updates one node per day at a configurable UTC hour, offset from the software updater's own schedule so the two don't collide. It also compares each node's blocklist domain count against its prior count after every update and flags a large drop as a probable partial-update failure (e.g. a blocklist URL that was briefly unreachable) — since Pi-hole itself gives no reliable success signal for that. Open source if it's useful for anyone managing more than one node.