Since nobody had the answer, I'll go back and look at the drafts. Here's every single Senior taken in the lotto since 2005:
2005 - Channing Frye - 8th
2006 - Shelden Williams - 5th
2006 - Brandon Roy - 6th
2006 - Randy Foye - 7th
2006 - JJ Reddick - 11th
2006 - Hilton Armstrong - 12th
2007 - Acie Law - 11th
2007 - Al Thornton - 14th
2008 - Jason Thompson - 12th
2009 - Terrence Williams - 11th
2009 - Tyler Hansbrough - 13th
2011 - Jimmer Fredette - 10th
2012 - Damian Lillard - 6th (technically a redshirt Jr)
2013 - CJ McCollum - 10th
2014 - Doug McDermott - 11th
2014 - Adreian Payne - 15th
2015 - Frank Kaminsky - 9th
Observations: Most of them sucked. Only one senior was taken top 5 (Shelden Williams). Only a few guys are notable: Brandon Roy, who was great early. Damian Lillard, who was technically a redshirt Junior and probably would have come out his real Junior season had he not gotten injured. And CJ McCollum, who took 3 years to show anything in the NBA, but was actually pretty excellent as a Freshman.
So based on that, I guess Brandon Roy is the one we're hoping for?
Roy had a pretty weak Freshman season: 6.1 points, 2.9 rebounds, 1 assist with 50%/10%/49% shooting. By his senior season he averaged 20.2 points, 5.8 rebounds, 4.1 assists, 1.4 steals with 51%/40%/81% shooting.
Meanwhile, Hield averaged 7.8 points, 4.2 rebounds, 1.9 assists, 1.2 steals with 38%/24%/83% shooting as a Freshman. By his senior season he averaged 24 points, 5.7 rebounds, 2 assists, 1.1 steals with 50%/46%/88% shooting.
Take that for what it's worth.