Setting aside comparisons to Holmgang, there are two design issues with Living Dead. First, anything that takes control out of the hands of the player is going to be poorly received. You can decide when to use it, but you have no control over the outcome. In single target, DRK has very little burst healing potential. It would be one thing if you could "fight for your life" and lifesteal your way through the healing requirement. But you can't.

The design interface also doesn't support the skill execution. Visually, neither you nor your teammates have no idea how much healing you require. If you have benediction, great. If not, frantic overhealing ensues. Wasn't the goal of the UI changes on Stormblood's launch to address issues like this to make them more visible and user-friendly?

How could this be redesigned? You hit 1 hp with Living Dead up? Walking Dead activates. You can't take any further damage for the next 10 seconds, regardless of when the effect is cleansed. Your attacks gain lifesteal, which allows you to help fight for your life (granted, 10 seconds is a very short time to do this, but it's still something). A black bar with a little skull replaces your HP bar to show you and your teammates how much healing you still need to ward off death. Perhaps consider dropping Benediction to 150 seconds so that you don't lose a recast every time you use the two together.

Build the communication and coordination into the ability visually, and give DRKs some degree of control over the outcome. Who knows? Perhaps we might even start to enjoy using our ultimate defensive cooldown.