I find it rather amusing that Holmgang got an extra 2 seconds added to its duration in 5.1 while Living dead went untouched yet again.

So we have one ability that makes you unable to drop below 1 and lasts 8 seconds with a 4 minute cooldown.
Then we have another that makes you unable to drop below 1, lasts 10 seconds, 5 minute cooldown and it will outright kill you if you don't receive 100 % healing during it. It's also easier to time for max duration because of the living dead > walking dead transition but harder to make use of that full duration because, you know, it'll kill you.

Any other invulnerability pretty much just needs enough immediate healing so that the tank can survive the next auto / mechanic. Also since I'm comparing LD to Holmgang as that is the closest comparison lets not forget that WAR can use Thrill, Equilibrium and Nascent Flash to recover HP if any of those are up at that moment. Thrill also gives WAR a 20 % healing received buff.

I think the most elegant solution would be to very simply remove the whole healing requirement + doom out of LD. Just:
Living dead: lasts 10 seconds, if you take a lethal hit activate walking dead instead
Walking dead: lasts 10 seconds, you can't fall below 1
Holmgang with 2 seconds longer duration and easier timing because of the living dead > walking dead transition offset by having that 1 minute longer CD. That's pretty much what it already is, so if it would be possible for it to not kill me that would be swell. As an additional bonus you would no longer die to a poorly timed Benediction either, because it definitely makes so much sense right now that it loses the beneficial effect too when you get healed.