You're correct in that evasion is theoretically worse at reducing damage than outright resistance, but it's still very valuable. There isn't any sort of "Attack type resistance" to compare it too, but it does have the advantage of negating any negative effects attached to the attacks you evade. Because of that it means it can be better against debilitating enemies (Ex. Tacticians), which I think makes up for the fact it's theoretically worse if you potentially get stunned.
My stance on evasion is that it's incredibly good for tanks AFTER you get proper mitigation up. Mostly that's because it scales well with normal mitigation and so you always have "Real" defense to fall back on if you get unlucky, including the unlucky scenario you get stunned through evasion/stun resistance.
The chart I made is just me trying to weigh things for a sort of general sense. You're right in that evasion could be theoretically weighed lower since enemies can take away evasion, but can't take away resistance, but I think that should be judged by each individual player. I don't think I could come up with a good "Generic" number for everyone. Sword/Shield players could actually weigh it higher because they can become stun immune and therefore evasion would be strictly better on average. Werewolf/Deer/Bat players can temporarily hit 100% projectile evasion, in which case mobs with ranged stuns (Like the elementalist trainees) shouldn't be an issue, but only during those times they hit 100% evasion and so it should be judged by the individual.
If you want to be simple/silly about it though, it's safe to say evasion has a 1:1 value with damage reduction, because 100% evasion to everything would allow you to dodge 100% of attacks and therefore take 100% less damage. This is probably not going to happen but it can theoretically boil down to that.