I wouldn't nerf the Amplifier, as nobody really uses it the way it is unless the server has a rare full-player spike, and only for cheese strats. I think it should be one-shottable instead of two, however. I have a set of class-based suggestions to make gameplay better as well:
Scout:
- Prevent the Force-A-Nature from getting crit-boosted, and perhaps also prevent it from getting minicrits too. Right now, if a FAN scout gets last-man crits, he's able to keep Hale away forever by barely shooting him. Not fun to play against, not fufilling to play as.
Solider:
- Buff the Bison.
- Buff the Equalizer.
Pyro:
- Give mini-crits (or crits) on the Flamethrowers. Pyro does painfully low damage, as he can't get close to Hale without spamming airblast and flare-jumping away, and there is little reward to actually use the Flamethrower as a weapon. This change could adjust that, encouraging Pyros to do damage using their flamethrowers.
Demo:
- Allow Demomen with the boots to regain shield over time, should they lose it. The boots are currently useless, as Valve made it where without the shield, the Demo speed boost from the boots is removed.
Heavy
- Needs more survivability. Going Heavy is a deathwish in his current form, generally netting little damage as well. I feel like he needs to be more fun, as camping in a corridor with an engineer or medic is the only way to currently play him. Perhaps nerf GRU damage, or add a new mechanic using fists?
Medic:
- Medic should have double-overheal. Other servers have this mechanic and it's pretty balanced. This could also solve Heavy's survival issue, but I don't think it's best to have a class solely rely on another to survive.
- Re-add Medic's ability on all Medi-Guns to rocket-jump with his pocket, akin to the Quick-fix. This used to exist on the server, but an update seemed to have removed it.
Spy:
- Increase the recharge time on the Dead Ringer or buff it's resistance. There's no reason to use it as is - as Hale can easily find you and kill you when it runs out, plus you'd already be put down to 60 hp.
- Remove the damage resistance on the Invis. Watch and give it a speed boost instead, which it had intitially, but has since been replaced. This made fighting invis watch spies a lot more fun and less infuriating, and also allowed for spies to get better access to backstabs.
This is all I have for now, probably have more later. Also, I support a change to Freak Fortress if it means better stability going forward, along with the ability for a few new bosses.