Most people agree that the hardest position to recruit for is DT. One thing that I think we can all probably agree on is that there has been a huge uptick in the quality of recruits at DT in particular, the last couple years.
While all the positions have seen an uptick, presumably from the IPF, I think that the addition of Jesse Williams also seems to have had a huge positive effect. His first year with Ohio was 2012, but I don't think his recruiting effect was really felt until the 2013 class.
Here are the players recruited as DT's, by year:
2004 - Jeff Browning (moved to OL), Landon Cohen, Jacob Williamson
2005 - Josh Leuck (movd to OL), Brian Mellot (left)
2006 - Alan Goff (moved to DE), Ernie Hodge, Marcellis Williamson, Pete Reese
2007 - John Flowers (moved to OL), Jeff King, Kadre Pinder (after JUCO, played OL)
2008 - Corey Moncrief
2009 - Carl Jones, John Taylor
2010 - none
2011 - Antwan Crutcher
2012 - Trae Clark (not eligible), Wade Wells
2013 - Tony Porter, Cleon Aloese, Cameron McLeod, Watson Tautuiaki
2014 - (grayshirt Frueauf, walkon Stephens)
2015 - Tony Arp, Sam McKnight
For most of the last ten years it has seemed that they were always trying to cobble together something that worked, and they often ended up moving DE's to DT, such as Neil Huynh, Tony Davis, Brandon Purdum, Corey Hastings, and several others.
The 2004 class had Cohen, then the 2006 class was good with Hodge and Williamson. 2009 added Carl Jones, plus Huynh who was moved from DE. 2011 added Crutcher. Thus, that was about 1 good recruit every other year.
Since 2013, however, the story is very different. McLeod and Tautuiaki have both been good, and Porter and Aloese look like they will be good, too. We haven't seen Frueauf and Stephens yet, but they seem to have potential, and Arp and McKnight impress me a lot.
It looks to me like the strength at DT will be dramatically higher than it's been for the last decades as the classes of 2013-2015 come into their own.