Talking about Oilers defense - Nurse might not be a great #1 D-man, but when healthy he's a lot better than the husk we saw last year in the playoffs.
As for the offense, I wouldn't hold my breath on McDavid & Draisaitl doing a repeat performance. They could, but they also could have very good playoffs and still not produce near to the pace they did last season. Also I have no idea what Draisaitl's injury was about, but the guy just put up 32 points in 16 games while averaging over 21 minutes of ice time, so I'm not sure how much better than that he can be while "healthy". Even though they are great players both of them, I don't think relying on two of your top forwards to average 2 points a game is the road to success.
They certainly could be a contender, but I'm not sure I see Jack Campbell as the guy that puts them there. Their goaltending was ok last year, not sure Campbell can be much, if any better. If anything, I'd see a healthy Nurse being the biggest difference. If they manage to play better defense as a team they could very well get that "improved goaltending", but if they play like they did last year, they'd probably make Vasilevsky look quite ordinary. I think their saving grace was they managed to force other teams to play their style of high event hockey and both McDavid and Draisaitl were scorching.