It's not primarily a balance issue. Living Dead is poorly designed on multiple levels. Incorrect mouseover tooltips, no UI element to show you the remaining healing required to cleanse the effect, cleansing WD removes your death prevention, loss of player agency. It's a long list. MagiusNecros noted that there's a certain DRK trust character who uses Holmgang instead of Living Dead, which goes to show that even the dev team doesn't think that it's reliable. The fact that it's obviously inferior to other invulns provides an opportunity to actually address the underlying design failure.

If you don't think that Living Dead has some serious design problems that need to be addressed, I'm really curious to know what stake you have in this discussion. It's hard to tell which job your concern is actually directed towards. If you're worried that PLD will be left behind, I think the simplest solution is to come up with three unique penalty conditions for GNB, PLD, and DRK that the player themselves is capable of working around, and set them all at the same recast.