I’m going with WR. 
Too many times we had drops in crucial situations. 
That’s not the QB’s fault, especially when it’s a well placed ball. ANY receiver should catch a good pass routinely, SEC caliber receivers should make the more difficult catches as well. 
Joe had his bad moments but the WR’s could/should have helped him more. 
Him throwing it too hard is BS!
NFL scouts love his powerful arm and ANY SEC receiver should aspire to make it to the NFL….