Not sure where you came up with him being a below average athlete. He's not an elite or freak athlete, but he's a good athlete, and in my opinion has better lateral quickness than Jackson. He's an inch shorter but still has good length. Also, remember that those measurements and weights are the same that were posted when he was a freshman. If you look at his body, he's much thicker than Jackson. He doesn't look skinny like Jackson, so he's likely gained some weight since his freshman year.
As to the conference he plays in, well they had the same questions about Lillard, C.J. McCollum, Stef Curry, etc. What I know is that he's played some of his best basketball against bigger conference teams, like Arizona or Vanderbilt. Another thing, Jackson was a one year wonder at shooting the ball from the three. His two previous years he has shot around 30%. Windler shot a tick under 40% his sophmore year, and over 42% his junior year. So far this year he's shooting just a tick under 39%. So I have more confidence in him being a good shooter in the NBA than I did Jackson prior to the draft.
Windler is also a better rebounder than Jackson and a good finisher at the rim. He's not afraid of contact. The only thing he has going against him is he plays for a smaller conference, and he's a senior. Other than that, if you can pick him up in the 2nd round, he could be a steal. Here's a video of his coach talking about him that might ease your fears a bit.
Here's another short video with some highlights from last season. As you can see he can play above the rim, he has pretty good handles and he's also a very good passer.