[Pudge]

Im not sure if I posted this suggestion already elsewhere, but I'll say it here again: instead of a variance, just stagger the spawns. When the server pops, only 1 or 2 raid mobs should be up. These should be random and unknown. Then, over the course of the next 3 or 4 days, at random times, the rest of the mobs spawn. Whenever they are slewn, their timer becomes a static 7-day, just like normal, until the next server reset.

This will keep mobs on a known timer, however spread them out over the course of days, increasing PvP and giving hope to the smaller guilds that they might contest 1 day, or maybe stumble upon a dragon a day or 2 after the server resets and assemble their army in secret to try and down it at a time the enemy might not have 40+ ppl on.