Viper was nerfed already. It used to have a diamond sword, sharpness one, and strength one, so imagine that. From my personal experiences, there is a way to combat viper:
When you are hit with the poison, you take a lot less knockback (you kind of don’t really move). I use that opportunity to combo the player back and force him to soup since I’m not taking knockback. By the time he’s done souping, my poison is out. Whenever someone uses viper, I find it particularly easy to kill them - but maybe that’s just me. The main thing that seems frustrating is trying to run away with each tick of poison slowing you down.
While to many it seems like viper is in a decent position as a kit, I’ll still bring your concerns up with others.