When I started hunting bosses a few months ago, tools like TibiaBosses and ExevoPan became really handy at helping me find bosses on their spawning time window, but it is really tricky whenever a boss spawn between the kill statistics update and the server save, because if will only show up and update those tools on the next day, which happens after the server save.
Because of that, whenever a boss dies on that time frame, I generally start looking for those bosses a day earlier. This has been proven effective several times when a boss was found a day earlier because he was killed after the kill statistics update.
My question is to people that do this for a longer time than me and may have more empirical data to back it up.
How are nemesis bosses cooldown tied to the server save and kill statistics update?
My theory is that they have an internal cooldown not tied to any of those mechanics, which means that once they die, a random seed is rolled and a respawn timer is defined abiding to a few rules for each boss, and they will spawn at that precise timer, even if the servers are offline, in which case a new seed is rolled, causing the rotation to be missed.
I believe this is true because of several occasions that high priority bosses simply fail to spawn on their time frame, or, for example, when we had the global rollback because of the level 2 reset, Abomination had spawned on Jacabra, and after the rollback, not only Abomination did not spawn again on that day, it completely skipped his 180 days rotation.