IMO the entire team looked tired at the end of the ISU game Having those 4 guys log 30+ minutes twice a week is (again IMO) a recipe for disaster; especially when you look at the last 7 or 8 games of the season.
What is the alternative? I'm not trying to be cute or argumentative, but really the only options would be:
Play bigger - use Kriener and Pemsl a lot more. I don't think the team is helped by this.
Play Evelyn and Toussaint a lot more minutes. Both of them will have to play more as it is to fill the void by Bohannon.
Playing 30+ minutes a game is a heavy workload, but it is done. Michigan went 15-5 in league last year, and had 3 guys play over 31 minutes a game, another average 29.6 minutes a game and a 5th (Teske) go for 28 minutes a game.
Michigan State had 3 guys play 30+ minutes a game and would have had a 4th in Langford had not been hurt. And their core guys got more rest due to more blowouts.
Purdue (a very deep team) had Edwards and Cline both at over 34 minutes a game, then 2 more over 25 minutes a game.
Wisconsin had 3 guys at 32+ minutes per game last year. Maryland had 3 at 30 minutes a game last year, and 2 more at 26 or more.
The workload is going to be a bit extreme, but I am not sure what other choices Fran has. I suppose if Patrick McCaffery becomes an option it would ease the workload, but I'm not sure he's even practicing right now. Expecting him to play meaningful minutes at a high level after sitting out this long would be unfair to him. 2 games a week is manageable if the practice load is lighter.