Hello,
I believe timers are associated with the actual mob not a zone so this would probably not be an easy change but can you give thought to changing the timer to 23 hours for guild instanced Tier mobs or at least the new releases?
The reasoning is the same that was used for the Polar Bear king change back on 12/25/13 -
Polar Bear King and Polar Bear Prince quests have been reduced to 23 Hour lockouts to help prevent the constant push back of the timer vs when its available.
Thanks,
Niix