I'll be curious to know what the "legit" assistance exercises are. But I tell you the attitude that there are maybe 7 total legit exercises in existence really bothers the hell out of me. Just in terms of shoulders alone your looking at some serious imbalances and impingement with that attitude. Ask someone in the know about exercises and injury, in fact, and they will tell you that lack of variety in movement is a PRIME culprit.
It reminds me of the last chapter of PP. Injuries are inevitable kind of thing. Everyone will get an injury at some point but NO injury is "inevitable". It may be damn hard to avoid any particular injury and you certainly can't ever make progress sweating injuries all the time but if you do get a serious one, rest assured it wasn't handed down from the mountain
. It's in your training and you caused it. And bangig out the same five exercises month in and out....should make it pretty obvious how it came about.