We're talking about improvements at the D1 level. Not a whole lot of guys are making huge jumps between seasons. The gains and improvements tend to be incremental. You're judging how good or bad they are off of one tournament last year. THat's also reliant on things like injuries and strength of the field. Those guys are all better wrestlers than when they got here.
Spencer is more diverse on his feet than when he got here.
Murin is better in nearly every facet, evidenced this year by his increased bonus percentage. Does that mean he will AA? No. He's not a super dynamic talent, and thus his margin for error against AA level guys tends to be small.
Kennedy is tough because we're judging him mostly from his high school tape given limited college experience, but those early years tend to be when the biggest jumps happen these days, and he definitely looks better than he did in high school. Look at his most recent win over BRaunagel. He put up 15 points while majoring him. Last year, Alex Marinelli beat Braunagel 4-1.
Warner you're already conceding so I'll move past.
If you don't see the improvements with Cass, I don't know what to tell you. He's wrestling a bunch better since he started, and one bad tournament last year doesn't change that. The body change is obviously the most physically apparent improvement, but he's pinning more people, putting up points, and reliably stingy on defense as well. You could make a fair case that Big Cass is Iowa's most complete wrestler (not best, obviously). He doesn't really have a "weakness" other than the fact that other wrestlers are also good.