It does need to be toned down, but the setup requires being able to hit and crit PvE mobs consistently and generally ends up very much not tanky at all in exchange for being able to hit/crit higher level mobs. Many, many people have complained of how tanky mobs in PvE end up getting later on, so we've ended up in a very polarized environment where we have some strategies that absolutely curbstomp PvE like the one mentioned in the OP, and the average person struggling to get decent clear times if they haven't optimized their build to deal with the insanely ramping up armor + DR.

The effect could simply be reduced for weapons that aren't the guitar so as to not completely remove the interaction all together. Since personally I'm getting tired of the pattern of entirely removing playstyles that are effective in PvE whilst offering zero alternatives until far later down the road. It makes me afraid to tell people how to make their build more effective in PvE for fear of someone deciding to be the whistle blower (like this thread) and having it get axed for being the most effective method.

Things like Umbrals being able to infinitely use Fade Out to prevent non-boss mobs from ever taking a turn with proper FP management or playing at night, or map-wide spells like Enma's Summons and Divine Shower making clear speed much more bearable in Spacey dungeons, or any dungeon with enough casters.

I'm going on a bit of a tangent here, but I seriously think we need to start thinking more about ways to make PvE fun and enjoyable rather than witch-hunting everything that makes it more bearable. All I hear are complaints from people who have played the game more than a month or two about PvE, and how it's basically just a gateway to making a character ready to PvP and interact with the world at large. That whole argument's for another thread though, I just think it's relevant when we're being faced with another potential nerf bat to an effective means of clearing most fights in PvE.

Back to the topic at hand, I'll simply list out the pros and cons of using a Quickdraw + Electric Axe build.

Pros:
Can instantly clear fights with the right setup and good (90-100%+) Hit and Critical chance.
Insane DPS with enough mobs nearby.
Deals Phys DR ignoring damage per critical hit.

Cons:
Suffers against mobs with innately high evade at later levels (Vorpal Rabbits, Corpse Hands, Feathered Serpent)
Is god awful against single mobs at higher levels such as bosses without enough adds to compensate.
Sacrifices defenses in order to deal optimal damage at higher levels. If the mobs live, you're probably going to die very quickly.
Uses a gun. Forgeries will annihilate you as fast as you kill them unless you're only fighting one and you've silenced it/can damage race it.

It's heavily shackled down by the fact it uses a gun. Guns are the most polarized weapon in the game in PvP. Having used this setup in PvP as well (MLM era), I can tell you having the hit and crit to deal consistent damage was not common. I could only take wins against builds that lacked crit evade and weren't dodgy enough to mitigate the damage I could do.

You're right, the infamous Burn Up > Winged Serpent > Lead Storm could be devastating in a team fight, but a Quickdraw Guitar isn't going to kill anyone in PvP. Unless the enemy team is full of idiots/sub optimally built players. All it takes is one Kensei and you deal 0 damage or better, kill yourself instantly. Even then, it's trivial to build the evade or crit evade needed to totally block out a QD/Guitar's ability to hit or crit.

Let me put it into numbers.

With my heavily offense oriented Quickdraw + Guitar build, I see about 110-120 Critical and roughly 250-260~ Hit. I cannot afford to put up buffs to boost these numbers outside either Scharfe or Focused Mind for minor bonuses to either Crit or Hit, and a rush setup would not do either of these.

With just Boneheart and the LUC you'd expect from a dodgy build (50 scaled) my Critical has already dipped to 45% or lower. The average Evade you see on dodgy builds is around 200-220 before buffs, so I'd have equally poor chances to hit an Evade centric build.

If my target is either a Demon Hunter, a Kensei, or a Black Knight, I've effectively already lost. Kensei can negate bullets entirely, BK can drop my Critical to 0, and Demon Hunter is a soft counter nowadays with Bullet Barrier, but enough that they can easily race me the remainder of the way from mitigating 25-30% of my attacks if not more if I fail to crit. To a lesser degree, Bonder/GS and Priest/LB will win if they get a turn due to their crit evade.