If you can go RB in the first I would be totally fine with taking Gronk second round. Its all about comparative value. You can still pick up great receivers in later rounds but there are only 2 or 3 tight ends that are elite. You might get a receiver that averages a point or two less per week if you pick a receiver 3-5 but if you pick a tight end that late you could really lose a lot of points. Having a player like that gives you an elite advantage each week at the TE position.