The next AA car is just as OP Firebar, it swaps the 2x 50cal for 2x cannons which still have the same potential firepower against that Tier.
I'm up to 3.3/3.7 now and I've got to break it to you that the Archer is painful to play. You drive forwards with the gun facing behind you which means you have to do 180 turns everytime you want to fire, you can imagine how that plays out when you get caught out!
The Crusader SPAA is where the AA OP dies out. It has the same 2x cannons as the previous armored car varient so you gain mobility but no additional firepower. The days of playing the Brit AA like tanks against ground vehicles has stopped