Hi. I've been playing the mod for a few weeks, and I went through all the weapons trying to find ones I think are overpowered. I think the mod is mostly balanced but there are a few weapons that are powerful even in the mod's meta. I tried to offer some suggestions without going overboard with changing things. I would make a pull request but I don't want to change anything without approval. Hope this helps.
Scout:
Geared-Up-Ghost
Increasing the Scout's mobility at the minor cost of having no secondary is exploitable by good players, who can ambush and run away from players much faster than usual. The 20% damage vulnerability is negated by the fact that most players cannot aim and shoot at a player with that much speed, and the Scout also has an easier time running to sources of health. Slightly reducing the movement speed and increasing the damage vulnerability to 25%, making the Scout's base health effectively 94 instead of 100, keeps the hit-and-run playstyle while offering a bit of leniency for lesser-skilled players to kill them easier. This also makes it less annoying to deal with scouts who only use melee.
To fix: Reduce 15% increased move speed to 10%. Increase damage vulnerability on wearer to 25% from 20%.
Soldier:
Crucible Long Sword
This weapon does too much in one inventory slot. 33% increased movespeed at the cost of -5 health drained per second is already extremely good. Combine that with being a very good melee weapon itself with increased range and the ability to gain health, there is no serious reason to use any other melee weapon. With the addition of the Maggot Multilator acting as a pseudo-Escape Plan, this weapon needs to be reigned in. I would recommend making this a purely damage-focused weapon without any mobility increases.
To fix: Remove 33% faster move speed on wearer. Remove 50% faster weapon switch.
Pyro:
Stainless Scorcher
The design of the new shotgun offers interesting tradeoffs, but it has been overtuned on release. A shotgun primary that deals high damage to buildings and other pyros while offering massive amounts of health for a small damage and range tradeoff makes Pyro get too much out of the tradeoffs. The range penalty is also counteracted by flare guns being able to light enemies on fire from a distance, where you can switch to the Stainless Scorcher and get free health with much longer afterburn. The fast firing rate, large clip size, and increased bullets from normal shotguns means there is very little downtime, and large groups of enemies can be lit on fire quickly, which further stacks onto the health regeneration. It's also silly that the health gained is overheal.
To fix: Remove "Afterburn damage is returned as health". Make reload speed the same as stock shotgun.
Propain
The old Axtinguisher is still very good even in the current nerfed state on custom servers. Making it deploy faster negates its main downside, which is that there is a delay before you get to use it. Removing its increased deployment speed is also an indirect buff to the few Pyro weapons with increased switch speed, similar to its old synergy in live TF2 with the degreaser.
To fix: Remove "This weapon deploys 50% faster".
Sniper:
Counter-Snipe
The "100% critical hit vs scoped snipers" attribute is overpowered. The Sniper's primary job is to kill other snipers, and reducing the skill cap to do so for no serious downside makes all other sniper rifles underpowered by comparison. The 40% increased damage combined with the ability to maintain a scope reduces the skill cap further by rewarding multiple bodyshots or uncharged headshots instead of a single charged headshot. Furthermore, being able to rapidly deal 175 damage to an enemy with no charge while maintaining scope is very powerful compared to stock. The ability to stay scoped in forever also removes the difficulty in landing headshots, so the 10% damage penalty on headshots should remain as a tradeoff for the Counter-Snipe's ease of use.
To fix: Remove 100% critical hit vs scoped snipers attribute. Remove 40% damage bonus.
Combat Crossbow
The main problem with this weapon is the ability to spam a corridor and put long-lasting marked-for-death minicrits on anyone who enters. Even in live TF2 the Jarate could only do this once every 30 seconds. This is because the crossbow has a very fast fire rate when unscoped, and because there's a fire rate penalty when scoped, there's rarely a reason to scope in. Retooling this into a sort of Sydney Sleeper weapon that puts minicrits on a single target provided you can land shots increases the skill requirement while making it far more fair.
To fix: Reduce fire rate to match the Hunting Revolver's. Make the fire rate the same when scoped and unscoped. Change marked-for-death attribute so it matches its description of actually only marking one target for death at a time. There is a similar weapon called The Marksman's Marker, so let that one have the ability to mark multiple opponents for death.
Ant-A-Jar
The Sniper can do a sort of rocket jump with the jar. This allows the Sniper to get to silly positions he really shouldn't be allowed to get to. The impact per map ranges from nonexistent to broken, but in any case increased mobility on Sniper for the minor cost of having no secondary for 13 seconds is too much benefit for too little penalty. Using the SPAS-12 instead of the Ant-a-Jar is good, but the jar jump lets you get to positions where no non-sniper enemy can realistically kill you, meaning there is no opportunity cost for choosing the jar.
To fix: remove self-knockback on the jar. If you don't want to do that, make it so that Sniper also takes damage and bleed from his own jar. This would make it easier to spam him out even in those positions, and it would also reduce the jar's ability to act as a panic button if he gets ambushed, since if he aims at the ground without thinking he just kills himself.
Striker's Shank:
Melee on Sniper is used so infrequently that it's pretty much irrelevant. Therefore any utility melee weapons on Sniper has to be assessed appropriately, since it will usually be an upgrade from stock. A knife that increases mobility is already good because it negates Sniper's main downside of finding new positions, but the mark-for-death penalty is too lenient because a Sniper can put the knife away a second before he gets into position, making it so there is effectively no penalty. The only downside is if the Sniper gets caught by surprise en route, at which point he would have likely died even with stock. Furthermore, since Sniper's main downside is mobility, giving him any escape tools negates this downside.
To fix: increase the marked-for-death penalty to five seconds. This way there's a tradeoff between getting to a position faster at the cost of potentially getting spammed out when he gets there.