Dude, you think he hasn't been learning striking in a decade of mma training that he has done?
He just doesn't have the natural disposition for it, or a may be just a slow learner. Some guys are like that. It is way too late for him to become a good striker, may be improve by 50% (which isn't hard at all when you suck that bad), but he is going to be limited going forward.
If I was his coach, I would try to help him become more defensively sound on the feet, but most importantly I would make him drill takedowns until he can takedown anybody, wrestle his ass off etc... At this point in his career you need to maximize his best skill which is his grappling and submission ability to the max.