With proper timing you can heap damage on Hedo and put him into his final phase. His mitigation self-buff was meant to train players into waiting... rewarding them with an opportunity to use powerful 'always proc' type attacks from our new weapons, etc. I don't see this as an exploit but a proper learning of Hedo's mechanics.

Accessing the zone, quest status, remapping, etc. doesn't have any relationship to Hedo's behavior, the mitigation buff period, or his "open for business" phase 2.
If I am missing something exploitative with regard to quests and zone access, please clarify.

Thanks in advance!