First of all, mock or no, they don't have 5 first rounders. They have 2 definetely. They have a good shot at 3. A very outside shot, imo, at 4. No way they'll have 5.
That said, 5 good players does not a team make. How many NFL players do they have in the linebacking core? How about the middle of the defensive line? How about the secondary? How about the interior offensive line? I would say 2, maybe 3 between all those units combined. And I'm not talking about 1st rounders either, I'm just talking about guys who will have an NFL career longer than 1 training camp.
And some of the players starting on this team not only don't have NFL careers ahead of them, but many of them would never start at any big-time program seriously competing for a national title (i.e. OSU, USC, Michigan, etc etc).
I don't think you can seriously say there isn't a talent gap between ND and teams like OSU & USC. I know Charlie does, but that's b/c he refuses to make excuses for his team when it loses, nor should he. I'm glad he takes full responsibility for a loss, even when its not truelly his to take.