Yall are letting the emotion of losing two important pieces of this defense sway your thinking here, at least for McIntosh.
McIntosh is in a situation where he likely will be drafted in the 3rd-5th round range. That is pretty good for an early entry DT. Secondly if he did return, he'd certainly get a substantial cut in his Playing time. That is just a fact due to Gerald Willis rejoining the team and Bethel likely improving on last season. Fact is McIntosh just has way more competition for his position than Norton does.
McIntosh - 682 snaps
Norton - 527 snaps
Moten - 260 snaps
Bethel - 197 snaps.
McIntosh is making a solid decision by entering the draft. If he returned and Norton declares, he could also face the possibility of playing out of position (if he had to be slid down to the 1t and willis playing the 3t), which could also hurt his draft stock.
Norton, I will agree that he should have stayed another year. He has barely any competition, and anybody that would be competing for his spot would just be replacing the snaps that Moten took from him anyways. So Moten is in a position if he returned to actually get an increased amount of PT (though he still would likely come off on 3rd downs and stuff). However, though Norton did not have the best season, he is still a talented NT prospect, and those are much harder to find than 3techs are in the draft. So it is very likely some team will take a chance on him. So I'd expect him to be a 5th-7th round pick. But he definitely could improve his draft stock this year.