At the end of the day players need to make plays and not only did McCord make plays but there were a lot of bailouts from Meeks, Pena and LQA. Of course the OC looks good when that happens. BUT, Nixon still called plays that made sense. Anea/Beck were trying to run 30 yard pass plays with a line that couldn't block and a QB who couldn't throw. I think early on Nixon also called a lot of deep balls when the line was struggling so he switched to a short controlled passing game. Nixon wasn't perfect (inside screen ugh) but he was darn good.
This season was the first I can remember where I think I said, dam that was a good play call, at least a few times every single game. I'm still in awe over the OT play call/design.
There will be bumps in the road next season but it won't be Nixon's fault. I'm confident Nixon will design the O around his players skill set rather than making players fit a system they aren't suited for.