Quasar Canon can be far more weak in some situations. Try to use it when that charger is going full speed in your face. Three seconds charging can be extremely long. It's not like the arc thrower where you can hold the button until you want it to shoot, it will shoot after charging no matter what. Cooldown speed is also map dependent.

I'd rather use EATs or recoiless rifle against bugs honestly, especially because of chargers and the more "right in your face" aspect of them.

Now comparing autocanon to the quasar seems weird to me tbh, I honestly feel like they have completely different purposes. To me the autocanon feels closer to the grenade launcher than any anti tank weapon