Last year it took less than a week for me.
I think it is (relatively) straight forward if diabetes is our only "complication". I strongly suspect it was close to automated for me. Put it this way, it is unknown for my GP to respond within a week so I very much doubt the DVLA contacted them.
It stills sounds as if the DVLA is slow if you need to use snail mail and paper forms due to extra "complications".