I did an experiment over the last three months. Instead of focusing on back squatting I focused on deadlifting and supplemented with something else.
Besides being conducive to competing soon, I wanted to try something different as my back squat has always been a point of contention, eg I have always struggled to maintain good form, avoid back pain, and make significant progress after hitting 315lbs. Also I noticed if I did not back squat frequently my form would change naturally. I've tried many variations, high bar, low bar, box, wide stance, narrow stance, above parallel, below parallel, parallel, etc and none seemed to provide a long term solution.
So basically, the back squat and I never got along so I tried something radical: I dropped the lift completely and replaced it with Zercher squats. I will say I have seen an increase in my leg and back strength and a big jump in my deadlift. In two months I got my Zercher squat to match my back squat (315lb) only treating the movement as an assistance exercise.
I also modified the exercise slightly by starting from a dead stop every rep (in the rack or in my case using a special implement) and using a thicker bar. I also learned to hold the bar a little different, holding my hands together and pulling the bar towards my rib cage instead of facing my fist upward(imagine giving yourself the Heimlich maneuver).
So who says back squats are the end all, be all. 100% first class bullshit. Maybe in power lifting they are necessary, but other wise I feel other variations are a much safer alternative to building strength.