Absolute rubbish! There is no such thing as a double-superior fighter in Aces High and that would be the only 'overly effective' change that should be avoided. The only thing drop tanks changes is range and range alone can only change where on the map combat takes place in comparison to where takeoff took place. The overall effectiveness of Spitfires in AH would remain unchanged.
"Fear me. I have fuel." Give me a break!
Regardless of whether you agree or not, it is clear, based on the fuel consumption multiplier, that HTC wanted a distinction between the short ranged interceptors and the long ranged fighters. A Spitfire or Bf109 can easily participate in an attack against a neighboring field and be able to return. With drop tanks and fuel management they can even go to a base behind enemy lines and return, but that is pretty much it if they want to be able to return. Long range fighters like the Ki-84, P-51, Mosquito and Ta152 can escort or range far into enemy territory and still be able to return home.
It is not that there is a double-superior fighter so much as fighters that are better suited to certain tasks. If you are scrambling to defend against an incoming raid, which of the following fighters are the best choices, Bf109G-14, Bf110G-2, Mosquito Mk VI, P-47D-40, P-51B and Spitfire Mk VIII? While you could use any of them, the superior climb/acceleration of the Bf109G-14 and Spitfire Mk VIII are going to give you a better chance of success in that circumstance.