From early on in the game I took a couple of "rational" decisions. One was that I found it so much easier to learn flying FAon that I wouldn't bother too much about FAoff. Today I can fly both, but I still prefer FAon. Likewise, I thought that gimballed weapons would, all in all, be an advantage for me, because I simply can't keep my target in the crosshair enough of the time. Using gimballed makes the crosshair "a lot bigger" so to speak. For me, it's all about how much damage I'm able to deliver in a given amount of time. If I land 5 shots out of 5 using gimballed, then it is more efficient than landing 3 out of 5 with fixed. Even considering the reduced dps of gimballed.
You might be a totally different pilot with different style and skills than me, so try the frags using both types (gimballed/fixed) before you start engineering. Try and see what works best for you in practice. You cannot judge that from numbers alone. You are definitely right that once you're close enough with every shot fired, fixed has more dps, but the question is if you're good enough to do that. I have a several thousand hours in the game, and I'm not good enough, but you might very well be