The throwing knife is amazing in PvP. It's brand new and will take the majority of people time getting used to it.
As someone who's spent years of my life playing games competitively and professionally, it feels fine.
Aside from the movement bug that makes it a little janky to throw sometimes. And the slow movement speed.
I would honestly give it ALMOST full movement speed. Part of the FANTASY of throwing knives is being quick, agile, and dexterous, not slow and clunky. Keep it below full movement speed to not be too crazy with it, but keep it close to full speed to fulfill that fantasy of being a knife slinging rogue. At least while throwing, being slow and creeping up on people with the Heavy feels fine, it's a stealth mechanic that makes you quieter and it does good damage. However I do think it should ONE SHOT people if you specifically hit them in the BACK, incentivizing stealthy plays with the Heavy. But these are just suggestions to make it actually feel more like what it probably should feel like. I do think it still feels fine as is, so long as the movement bug gets fixed quickly. Heavy Stab is high damage, throw is high enough damage to 2 tap people, the shank is weak, but it's supposed to be weak since it has no attack delay like the sword. It's not a melee weapon it's a ranged weapon.
Eye of Reach + Knife is my new life. It's such an amazing combination.
Do I think the EoR+Blunder combo is still the king? Yes. But we have a couple of new solid additions to shake things up and make the game more interesting and fun.
As for the Double Barrel, it feels okay when used for PvE, but so far feels NEARLY worthless as a PvP weapon. There is no reason to use it over an EoR or Flintlock. Using it in place of a Flintlock does give more damage per reload, but you have 2 less reloads and it requires you to be more accurate with 2 shots rather than just 1. If you miss a second shot, you're now doing less damage with less available reloads. Using it in place of an EoR is just a nightmare, it's gonna HitReg more because of it's slower projectile, it barely does more damage which again requires you to land 2 consecutive shots instead of just 1, and really just feels like it wasn't made for PvP but more for PvE. So far it's a monster in PvE.