He did technically underperform his recruiting rankings that were something like 3, 3, 3, 7 during the four years he was there, but he did have a winning record each season, along with 4 straight bowl wins in the Texas Bowl, Sugar Bowl, and Alamo Bowl x2.
He's an elite recruiter and a pretty good coach who did have success at a blue blood program, just not quite the success that program expects. Others have stated previously, but I don't think you can just brush off the idea of the Texas boosters meddling in recruiting, strategy, coaching hires, etc and the effect it has on that job.
However, my question is about some things I've read about him being universally despised by Texas High School coaches, at least according to a guy over on 247 who says he's a Georgia fan, and claims to know some things. Apparently, he is/was banned from a few HS programs down there, which played a part in his firing. I'm not sure if I fully believe all of that, and think he stance toward the racist "eyes of Texas" situation probably played more of a role in the good ol boys club wanting him fired.
Regardless, the Texas job is just a completely different animal. Could Herman get CU recruiting in the top 30 consistently and back to 6-7 wins/year? I think there's overwhelming evidence to suggest he could.