If you feel T3 is underpowered versus T4 and you fly Dola, that would be the main cause. The other ships are capable of punching back. All except Dola.
I highly recommend getting the Jump Drive eventhough it is not a prerequisite to unlock T4's down the line.
That or ditch the ship. Save yourself the suffering and grind the other ships in T3 until Devs do something about the Dola.
T3 Medium Destroyers are fun.
I switched from Dola to Ceres (T3 Aion). Now I am half way down to T4 and don't regret it. Very fun ship to fly.