Honestly outside of Willie, Degen, Aaron Holker and Kevin Jackson I can't think of many transfers including Juco's that have made a big impact for us. Here are some off the top of my head.
Duke Burk - Came from N. Illinois as a R12 guy, i don't think he even made the R12 in his 2 years here.
Nate Carr Jr - Came from Iowa Central (JUCO), i think injuries played a part in him not doing as well in his few years.
Chris Drouin - Came from Arizona State as a former AA, I think he qualified for the NCAA tourney with us,
Matt Gibson - Was at a Juco in California, he ended up AA'ing his senior year
Phil Hawes - Came from JUCO, not sure if he even hit the mat for us.
Patrick Hunter - Came from JUCO. didn't do much for us
John Nicholson - Transfer from ODU, never made NCAA's at ISU, but qualified 2 times at ODU.
Earl Hall - Kinda a transfer came from OTC 2xAA
Pat Downey - Transfer from JUCO, We all know this story, 1 x AA at ISU
Danny Bush - Transfer from IA Central (JUCO), won a few matches for us
Skylar St. John - Transfer from Iowa, injuries cut his time here short
Todd Small - Transfer from JUCO, qualified for NCAA's
I may have missed some older transfers, but this is recently. So we've had a few guys that contributed, but nothing earth shattering. Not saying we shouldn't look at transfers, just saying a transfer probably isn't going to majorly change our program (unless we got like a Woods, Griffith or Wick type of guy). So i think what Dresser and Co are doing is what we need to do, get some freshman and develop them.