My suggestions for making the game better :

Medic :
add 2 smoke grenade to medic
make medic more useful by charging the item 1 time to get it active for 3 revive or 15 sec max

Assault :
nerf assault weapon by adding more recoil
increase C4 throwing distance

Sniper :
sniper have to one shot
increase bullet speed

Other :
change the stupid shotgun of other classes because the map is really not appropriate for shotguns
nerf tanks a little by making them more slow to rotate turrets