Sorry but ermmm...misused? The concept of a fighter that actually has to let the enemy get on it's six, and defend itself with four rifle caliber machine guns, while the opposition is cannon armed, is rather silly.
It couldn't even shoot at something in front of it!
The Defiant was NEVER intended to be a Fighter vs Fighter machine. It was designed, built, but not employed, as a formation Bomber Destroyer operating with an escort. Therefore, your statement:
"The concept of a fighter that actually has to let the enemy get on it's six"
is so wide of the mark as to be irrelevant. Moreover, your other assertion that the Defiant had:
"four rifle caliber machine guns, while the opposition is cannon armed"
seems to miss the fact that all UK fighters were armed with "rifle caliber machine guns" at that stage, albeit 8 of them. A more relevant point is that the Defiant's gunner could keep a target under fire for a lot longer than a single seat fighter as the size of the guns' engagement zone was far larger. Consequently the weight of fire was probably similar. Finally, your line:
"It couldn't even shoot at something in front of it!"
also leads me to believe that you consider the Defiant to be an Air Superiority weapon, which it wasn't - nor was it intended to be. It could, however, engage a target that was ahead and slightly above (ie in the age-old Ideal Killing Position) without exposing itself to the return fire from the usual rear or dorsal gunner and presaged the advent of Sträge Musik by at least 2 years. By offsetting the attack to one side also allowed any ventral return fire to be avoided too.
When employed correctly (see my posts in
http://www.ww2aircraft.net/forum/aviation/boulton-paul-defiant-7448-2.html) it could put up a creditable performance. When employed in 'penny packets', without support, it was always going to be Dog Meat.