Islearth, you are trying to imply that those 4 people are hunting all the time in places where Demodras spawn? Because you looking at data where he is killed- you missing part where he spawned and he have not been killed. Each location can have different spawn timing. Some of this locations are not visited for months! You would have to reach out to the person who is slaying those mobs- is he hunting in one particular spot etc etc. Or check it yourself by going those spots and providing screenshot.
But also, If you check stats for Bastia- which would have less people interested in doing this task, 30 days seems to be "repeating" theory.
It is bit sad that screenshots on Tibiabosses are not upload with the date when the boss was killed. But pretty much screenshot from
https://www.tibiabosses.com/forum/topic/the-great-boss-hunt-2021/?part=150 is 02/12/21 (after new update and it was uploaded on 03/12/21), which makes you Islearth another spot to check on Dibra ;-) GL