How powerful is an increased crit range?

[SodaDarwin]

As title says.
Additionally, optionally, increased crit multiplier.
Idea is, Chaos Knight kinda class where one of the benefits is getting boosts one or both at certain levels, such as 1st, 5th, every fifth after. This could result in, say, a greataxe with crit abilities of 15-20/x3. Or x8. Or something along those lines.
So yeah, on its own and factored with other things, how powerful is an improved crit range/multiplier/both? Or is it such a matter of optimization that it's pointless to think about it on its own?

[Emperor Tippy]

Depends on the build, the amount of increase, the weapon, the level, the group play-style, and a number of other factors.

For example, do you already do seven hundred damage on a standard action attack with a minimum damage roll? Well that is enough to one shot pretty much any monster published by WotC so having any more damage is pointless.

Or do you deal most of your damage with static bonus damage? If so then an increased crit rang means that you are more likely to get double/triple/quadruple that damage while if you deal most of your damage with dice rolls a critical does very little as bonus dice aren't multiplied.

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At its most basic, every 1 point increase in threat range is a 5% greater chance of threatening a critical hit.

And yes, thinking about it on its own is mostly pointless.