Holmgang has been overpowered since 2.1. It was even more overpowered when it was a 6 second death prevention ability on a 3 minute recast with knockback prevention and immobilization (and the capability to interrupt uninterruptable abilities, but that was a glitch). Standardizing it to a 10 second duration and 4 minute recast actually made it weaker. It's just that the less astute people in the room finally started to recognize that Living Dead was objectively inferior.

As long as invulns are designed with differences in mind, players are going to perceive them as having more or less value. To me, the single most important factor in an invuln's design is its recast. If you lined up Hallowed, Superbolide, and Holmgang up and asked me to rank them from best to worst, it would be:
1) Holmgang
2) Superbolide
3) Hallowed

To me, Superbolide is a better HG. But if Hallowed had the same recast as Superbolide, why would I ever want Superbolide? If Holmgang had the same recast as Superbolide, why would I ever want Holmgang? It doesn't matter if you can negate the downsides of an ability with planning. You always have more flexibility from not having the extra drawback in the first place. If you can't tolerate any sort of difference between the abilities, then you have to either homogenize invulns into a role action, or get rid of them altogether. I'd actually much prefer the latter, to be honest, but I know for a fact that many people would disagree with me on that.

Imagine for a second, if they reworked Living Dead such that it did the following:
When you prevent death, Walking Dead activates. A black overlay shows up over your personal and party HP bars showing your healers how much HP is left to cleanse. Even when that criteria is met, you still have the death prevention effect running for the full 10 seconds. And you set the recast at 3 minutes, which syncs perfectly with the likes of Benediction. Would you go for it? I think that lot of people would. I personally wouldn't enjoy that design route unless DRK was specifically a lifesteal tank, because I like being in complete control of my own ability. And I think that given that DRK is more focused on damage prevention than it is on recovering HP after the fact, it probably makes sense to have an ability that is closer in design to Hallowed than it is to Holmgang.

If it really bothers you that much, though, just give Hallowed its own unique drawback and adjust the recasts accordingly.

I think that as long as players have differing opinions on which invuln is best (assuming intellectual honesty in the discussion), then it's fine for them to have variations in performance. It's really the consensus that you should be worried about. When most people agree are able to agree that one invuln is terrible, then that's a big red flag.