Holmgang need a range increase.

[Rhyn]

that is what war pays for a short cd invulnerability......

Hallowed Ground - complete invulnerability for 10 sec.
Living Dead - can't be reduced below 1 hp for 10 sec. I have never seen the walking dead status matter, ever.
Holmgang - can't be reduced below 1 hp for 6 sec. Needs a target. You are immobile and can't dodge that telegraph that is assuredly coming for your face.

There are plenty of downsides to justify the shorter cooldown already. Having the ability straight up -not trigger- when you need it because you fought a boss at a normal distance instead of inside him should not be one of them. Yes that is hyperbole, but I've had Holmgang not trigger so many times at a normal fighting distance.

Why would you even not be within melee range from the boss? I really can't think of any situation where I'd want to holmgang away from a boss.

It's 6y to the center of the mob. While other attacks don't seem to work this way, so you normally fight a large boss outside this 6y range.

[Lyth]

...

I don't think this is correct. I've used Holmgang on both Bahamut and Alex back when it was cool to do so, and I haven't yet run into distance issues even when standing at the edge of a large boss' hitbox.

Actually, there's a reason why you don't want a very large radius on Holmgang. It has a hidden function: you can reposition mobs and interrupt some actions that would otherwise be interruptable by activating Holmgang and jumping outside of its active range. This causes the game to pull the mob/player towards you, in some cases interrupting its cast. Historically, the only way to interrupt a Dreadwash cast in Leviathan Ex once it started was to Holmgang jump it. Holmgang also negates knockbacks in some cases, which is another reason why the range check is handy.

And here we all thought it was just an invincibility move with the recast of Sentinel.