"The Hawkeyes bring back only 12 starters, tied for 9th-most in the Big Ten" Yes, but Iowa brings back a pile of guys who had significant playing time but didn't start enough times to qualify. It was the first year of significant playing time for many of those same players. I would put significant odds that the majority of those players will be significantly improved from last year.
You could turn this on its head and list the starters who have little or no playing time at their position.
P - Colten Rastetter ? Possibly the only RS Freshman starter on the team. Senior from Central Michigan transferring in.
PK - Recinos or Ellis ?
FS - Brandon Snyder - Walk on
WLB - Aaron Mends - I look for him to be a standout player.
RT - Ike Boettger - Only a handful of games as starter before going out with an injury last year. Otherwise has been starting RT through two years of practices.
FB - ? Iowa can usually find a few blocking fullbacks.
WR - Riley McCarron ?
SE - Jerminic Smith Saw light duty throughout last year.
There are several candidates for WR along with Smith & McCarron
That's a pretty short list of inexperienced starters. Many of the other are under the threshold for starts and playing experience, but have played quite a bit at their position or a similar position.
The only this publication can state that Iowa "only has 12 starters" is if you do things like count Ott as a lost starter, even though Iowa played more games without him than with him last year. Let's go through the list.
Offense
FB - Iowa will have a new FB. Cox and Pliewa were good, but Iowa has replaced fullbacks many times.
TE - Krieger-Cobie gone, Kittle in. Is senior year Kittle going to be better than senior-year Krieger Coble? Probably. Depth will not be as good, but Kittle can play.
OL - Iowa loses both Blythe and Walsh. Both good players. But every one of the presumptive starters will have started multiple games in their careers already, including Daniels. Croston, Myer, Welsh, Daniels and Boettger is solid to very good.
WR - replacing T. Smith. J. Smith started twice last year, including a 4 catch, 100-yard game against Illinois.
So on offense, the only place Iowa will be starting a guy who never started a game before is fullback. Do the same exercise with other West teams and I think Iowa compares very favorably.
Defense
DL - Johnson and Bazata are starters. Hesse should be considered a returning starter, he started 8 games. Nelson is the new starter and he played a lot of snaps.
LB - Jewell and Nieman returning starters. Mends is new, played a lot of special teams.
DB - Taylor, Mabin, King all started at least 13 games. King didn't start the Nebraska game as he had to sit out first quarter. Snyder is new starter but played ST.
3 new starters, with only 2 of them (Mends and Snyder) having not played a lot of snaps from scrimmage.
If the team name was Nebraska or Wisconsin and they had this amount of returning starters (including the second team all-league QB and the best defensive back in the country), they would be the heavy favorite for a division title. But since it is Iowa, they are not. To be fair. Iowa has performed poorly before with high expectations.
Biggest concern to me are the specialists. Brand-new guys punting and kicking. I wouldn't be surprised if the 5th-year transfer from Central Michigan wins the punting job.