[Kameron8]

...omitted for brevity...

I fundamentally disagree with a few points you've brought up here.

There's a reason people say Lightning Kensei is the only good Kensei. The other elemental impacts are fairly lacking in comparison to lightning when it comes to Kensei, that's right, but they're also not too useful in general. Specially Quaking, which has it worst.

If Lightning gets too nerfed, Kensei enters the territory of 'weak class' once again. Onto the main point, though.

Or even removing your critical rate through debuffs, or simply not allowing you to have the momentum to crit combo into Wazabane > Hirazuki.

The topic shouldn't be framed as an issue with Kensei -- it isn't, it's an issue with the disproportionate damage output lightning criticals do when compared with almost everything else in the game. Kensei is excellent at leveraging lightning criticals, but the logic should never be to leave a broader system (lightning criticals) alone because of narrower impacts with something else entirely (Kensei will be bad without lightning criticals). If a class was only able to function when using a single mechanic like that, it's a class that needs fundamental changes, not to keep its crutch. This also applies in reverse: we shouldn't keep a broken system as is because one other outlier is comparable (e.g. Custom Seed spells). Both should be addressed.

As it stands, classes who can use two-handed swords with 140-170 Scaled Weapon Attack obviously benefit more from lightning crits than classes that use tomes or non-two-hand-viable weapons.

If lightning criticals become far less threatening, then people will feel much safer ignoring their critical evade entirely in favor of more general DR again. Critical builds should hurt people that they can crit, but that's my opinion.

I don't disagree with the premise that critical hits should hurt people with no critical evade. However, how easy it is for critical builds to crit and how much they hurt them when they do crit are the two points of interest as far as the thread is concerned. The critting autohit system is far less risky than Evade vs. Hit: instead of risking a miss entirely when trying to crit your counterpart, Lightning Crit vs Crit Evade's stakes are risking doing less damage or getting lucky enough to dunk the guy for almost double damage. The counter doesn't always accomplish something, and when it does, it's far less impactful than its counterpart (dodging a basic attack completely).

Most lightning crit autohits do lightning damage, which are also cushioned by anyone running a decent amount of lightning resist.

Lightning is one of the hardest elements in the game to resist, since it's one of the few without shoes or accessories that provide 30% flat resist. Outside of (likely) tanking your build to wear a Beldam Aegis, the best you're going to get is materials, Cloaks of Many Color, Sanctity, and maybe a class-based resistance if you're running something like Lantern Bearer.

Additionally, the implementation of Soaked gives the element a unique means of fighting the scarce resists, if the lightning user uses or teams up with Tactician/Spell Thief/Ranger/etc.

And if lightning were to be hypothetically nerfed to the ground, people would just move on to the next thing.

This is inevitable regardless of what good thing gets nerfed. It doesn't mean overpowered things shouldn't be nerfed, the goal is to shorten the distance between the best things and everything else, so the difference isn't so glaring.

TL;DR:
Issues:

• Lightning crits do too much damage compared to other autohits.
  
• Lightning crits offer more damage than basic attack crits, without inheriting the risk of missing an evasive target completely. Basic attack crits have the worst of both worlds.
  
• Elemental Impacts are so powerful that it's almost unheard of to run autohit-centric classes without them, where supported.
  

After saying all of this, though, it isn't as though I have some magical fix to the issue. It's extremely volatile to try and change only damage numbers on a % multiplier. I don't think making Evasion beat it out is the best idea, since Evasion-ignoring attacks like Kagekiri exist, and Knockdown removes it outright. I'd honestly rather see lightning's Elemental Impact change to be something beside critical strikes. I'd also like to see people not so harshly punished for not including elements in most builds, but that's a topic for another time.