On defense, Oregon State wasn't great on the peripherals - not a ton of sacks or TFLs, allowed too many explosive plays - but on the whole they were solid against the pass and run and very good on 3rd downs. Though not elite on defense, the Beavers were in the next tier and 14th in schedule-adjusting EP3 allowed.
On offense, the Beavers could run and throw, but they were terrible on 3rd downs. Oregon State was fairly explosive and great in the red zone and kicking field goals. In other words, they often needed just one play to get them in scoring range and then they were dynamite once they got there, but they should have been better at maintaining drives.
The Mannion/Vaz thing still isn't settled (as of writing). Vaz was the more efficient passer (25th in EPA+/pass), but statistical difference between the two can be traced back to one start, Vaz's first, when he thrashed BYU. Oregon State needs someone to step up and excel behind center, because those areas where they did succeed in 2012 are less predictive of future success. But the defense should be good enough that a decent offense will keep them competitive.