The culprit is likely none other than Yoshi-P himself. We memed back in Stormblood that the reason why BLM was so powerful was that he mained it, but showed during live letters he couldn't do a rotation to save his life, so we joked that the devs buffed it to high holy hell for his sake, but the jobs he didn't main were de-prioritized. This was only partly in jest at the time.
Starting in SHB, the team stopped putting out the job change patch notes ahead of time, to prevent the community from complaining about the changes before trying them. MNKs still complained and the fixes they asked for (especially with regard to Anatman) were not listened to for two expansions straight.
Then the live letter for 5.4 happened, and it was practically admitted. Blue Mage got the Suzaku kick MNK wanted, MNK got a third of its kit - which it still had - rendered completely useless, and Yoshi-P outright said on camera that he considered himself a "white belt" at the job.
Viper is 4.4 MNK in a tighter package, with some of the fixes us "black belts" wanted: the Demolish and Snap Punch combos consolidated to one button each to make more hotbar space without losing anything, changing the resource gauges from all-or-nothing meters with shallow payoffs to multi-move spectacle-fests during our bursts, an unshackling from Samurai gear stats that were unfavourable to MNK's balancing, a chakra gauge that isn't tied to RNG (which no melee DPS should have), a Greased Lightning gauge with an instant stack button (the requested Anatman fix asked for in 5.x) and that wouldn't shaft speed or power when tornado kick (Uncoiled Fury) was used, a Dolphin Flurry (Reawaken) combo, and more. It's still simplified, but it's something that MNK mains from back in Stormblood could stomach as a good foundation to build off of in future expansions, instead of what they did to it in EW.
And no matter how much people begged for the dev team to fix it... it not only didn't get fixed, IT GOT WORSE. EW never reversed course on what they did to MNK, it just doubled down on it.
If you saw the trend of what happened to MNK from SB onward... you know what's coming for Viper, and I'm pretty damn sure it's Yoshi-P himself who just can't play it well, given the history of what happened to us MNK mains.
I quit after 5.4's patch release. It was infuriating to the point of driving me away. I will do so again if they do not reverse this decision, since the game will be ruined for me, and I'm going to encourage both the review bombing of Dawntrail (which already has a terrible story) and striking of DPS mains since pretty much all DPS jobs are suffering from the precedent that was set with MNK changes from 5.x onward. Again, I can't say it enough; people need to apologize to Stormblood MNK mains since now everyone else is experiencing what we went through for the past two expansions and now you all know how it feels.