I can hardly image how "speeds of approach" can be unrealistic 
Somebody really need a math.
At the risk of proving that I speak Tard . . .
The closing speed of any fighter in this game and, say, a box of three B-17s is, in fact, too slow. The reason has nothing to do with the fighter, but rather has everything to do with the bombers.
Bombers during the war flew at cruising speeds that were often 80-100 mph slower than their top speed. They did this to maximize range, maximize the life of the engines, and to make flying in tight formation safer and easier. They did not routinely increase speed when attacked by fighters, either. They remained large,
slow targets.
In AH there is no such need to maximize the life or range of your box of bombers. So, the bombers fly with the throttle firewalled -- and therefore at speeds far in excess of what the real life interceptors had to deal with. They are still large targets, but not nearly as slow.
Thus the original poster's complaint about closing speeds. Unlike the bombers, interceptors most certainly would firewall the throttle so as to minimize the time inside the bomber's gunner's range -- thus closing speeds were much higher than you typically see in AH.
My personal opinion is that bombers are easy enough targets as it is, and there is no need to 'dumb down' their speed overall. I have, however, advocated truing up the speeds of the drones, i.e. take away their ability to "overspeed" and catch up to your lead bomber if you start to leave them behind. Make the lead bomber slow down so the drones can catch up. This will have the overall effect of making the bombers slow down when they want to maximize their firepower with a tight box, and make those "closing speeds" more realistic (even if only slightly).
