1. Give it the HG cooldown timer (One of the longest)
2. Make it so you can turn it on like tank stance with no expiration
3. upon taking a blow that would kill you the cooldown timer triggers and you get walking dead
4. You then have 10 seconds to press the inlvun button which has turned into "back from the dead" or something like that manually which brings you to full health
5. If you don't do it in time you die

this sounds like a unique take on a invuln with some nuance and skill expression and it makes it incredibly useful as its the one invuln that procs on death.

Also seeing as its pretty OP it does deserve a longer CD timer like PLDs

I think this would be vastly better.