This guide will assume you are familiar with the Heroic version of the fight and expand on how the fight changes in Mythic difficulty. If you are not familiar with this encounter, check out our heroic guide by clicking the button below.
Like many other fights in Uldir, there are very few changes to Zul on mythic that impact healers. The only one that really matters is the Pool of Darkness applying stacks of Corrupted Blood. This means you will need to add a little more priority healing to people who are soaking Pool of Darkness. As a shaman you may need to purge Decaying Flesh off an add to force it onto another add to permanently kill an add. The jump order for Decaying Flesh is always Crawg to Bloodhexer to Crusher.
Notable Azerite Traits
Look for any traits that improve AoE healing. Overflowing Shores, Sprouting Spirits, and Swelling Stream are all excellent choices to fulfill the need of AoE healing. Ancestral Resonance has potential on this fight if someone else can use Bloodlust / Heroism on pull so you can get a large mastery buff in the final phase where healing actually matters. Ebb and Flow has potential since the entire raid is stacked in the final phase.