Its my personal preference. Jp4 dies without chances to firefly (it really easy to land rockets on it plus jp4 without vet has only 640 hp, which, if i am not mistaken, one shot from rockets landed on top of opening ff shot).
I still think in terms of raw at nothing comes close to command panther for mark target spam and jp4 combo. But its 2 tanks.
ultimately this is more due to the tulip than the Firefly's main gun.
I do agree that the tulip is very powerful and would prefer to nerf it. The firefly should be more about the main gun and chassis than some rockets strapped to its turret.
I know munition problem become semi-trivial in a large team game, but it's not fair to the british if their primary TD is dependent on a 100 mu ability that require a 50 mu upgrade.
balance the unit itself first, then balance the ability.
and the Firefly's slow rof is for a reason. The unit's high penetration and high accuracy make it useful against heavy tank but its low rof keep it vulnerable to medium tanks. It is for the same reason why the jackson only have 480 hp.
The Firefly's low rof keep the panzer 4 and stug relevant against british late game.