Wasn't really sure where to put this and can't put the link on because it is ESPN Insider, but Mike Sando did a survey with 26 sources (2 HCs, a bunch of DCs, some talent evaluators, etc) and asked them to rank QBs on a scale of 1-5 (1 being elite, 5 being awful).
Tannehill ranked 23 out of the 32 with the average score being 3.32.
The comment that stuck out to me was a defensive coordinator saying he is a game manager where everything has to be right for him to be OK. Not the best arm, not the best release and when his team played they didn't fear him.
Only other comment was a pro personnel guy who said Tannehill should be in the 2nd tier (where average score would be under 2.5).
Guys who were below Tannehill: McCown, Schaub, Henne, Manuel, Cassel, Hoyer, Fitzpatrick, Locker and G. Smith.
Guys just ahead of him were Bradford, Palmer, RG III and Dalton.
That sounds about right to me, he has a lot of minor issues, most of them are coachable, the real problem is the amount of issues, none of them major but enough of them so that they as a whole are a major concern, footwork, reads, anticipation, seeing the rush, accuracy and leadership are all areas of concern, it's a lot on your plate to try to improve in each area.