Couldn't you just do a "need to sync" check using one player entry. For example: Every client would reply to a sync check with the player in their DB with the newest timestamp, resolving ties by ordering alphanumerically and picking the first. If you don't match the player and timestamp then you're out of sync.
Is broadcasting a two way process? For example, in the kara example, does just one leader need to broadcast or does each kara leader need to broadcast in turn?
If both need to broadcast, then this method will falsely indicate that they are synchronized after the first sync.
Yah, each Kara leader needs to broadcast their own changes; or, one of them has to initialize a full-sync.
Another option for detecting whether two databases are in sync is the checksum that's tracked in the points database. If two checksums are different, then there's a difference and a sync should be done. Of course, even that might not work if the two Kara runs awarded and deducted the exact same # of points (which is likely in non-auction DKP models).
Hmm... I guess some sort of hash that includes player names & their spent/awarded point totals might be able to be calculated, then used as an indicator for whether 2 databases are synced.
edit: Don't worry Astaldo, that feature isn't going anywhere :-)