From my experience the weapons are either balanced or underpowered, which i'll be looking over the underpowered ones
'Akbar' - The weapon has been nerfed too hard after the tier drop, not only is it outclassed by the rest of the T3 weapons but some T2 have similar performance, needs a damage increase.
'Tempest' - It's really bad, one of the least used weapons in the game that being because of it's terrible ammo efficiency due to the low damage output (for a pistol)
'Quicksilver' - There are cheaper alternatives like the Deagle or the Stabber that have similar performance, clearly underpowered for a T4 weapon, should have its damage increased or 'takes half the ammo' stat.
'Hephaestus' Tau Cannon - Not having to reload and offering the ability to charge shots can be really beneficial, even with that the weapon struggles to deliver enough DPS compared to the rest of the T5 weapons, simply having it deal full headshot damage should make it decent (since what was mentioned makes it special in a way)
M2 Carbine - I think the majority agrees that this weapon sucks, making it use AR rounds should have it on par with the rest of the T5 weapons (less firerate than the Scar and accuracy on full auto, no pulse point multiplier like the Adonis)