You've been burnt, your buying the wrong stuff. Corona servos, they are horrible. RJX look alike head systems too much moving parts has more chance of slop, no room for simplicity. Assan gyro? The worse gyro to buy. Your going the wrong way in things. This is what I mean, you got too much on your plate, it's clouding your mind.
This is what I buy servos that are proven they work well. HXT900's, XGD's, Hitecs, (I've seen these servos doing smack 3D, you gotta have a gyro that supports a lot of different kinds of servos). DFC head and swash designs, pure simplicity, I add Trueblood dampers for crazy flying. As for gyros I use spartan quark, beastx v3 or clones, vbar or clones. Mainblades I use carbon fiber PRO3D and Radix clones(once again proven in smack 3D just check on youtube there tons of videos with them). ESC's I use YEP's for my 250 and 450s. They all work well.
I've been down that road before, buying all sorts of crap, expensive or inexpensive. There are crap things out in the market or over rated. You just got to make sure you don't get sucked into buying them, and making sure you are buying the right rigs