Yeah, OL are a bit odd. Technique is easy to see, which is why guys like Zack Martin looked soo appealing as prospects. And athletic talent is easy to see, which is why guys like Laremy Tunsil looked so good coming out. But the speed of the game and the complexity of both defenses and offenses sometimes makes it tough for guys with the athletic ability to keep such a high rate of technical excellence to grade out as a good OL. That projection is really really hard, and part of the reason why so many OL prospects bust. The job is incredibly physically demanding, but also is one of the very most mentally demanding positions as well. Couple that with needing the vision and experience to read the play as it develops ... it's a lot to process and a lot of instant decisions to be made.
Remember, OL win the vast majority of plays, so a kid winning 70% of the time looks bad because you're seeing him lose 30% of the time ... despite the fact that he usually wins. Some guys can win 90% of the time but are physically overmatched that 10% of the time because they lack power or lateral quickness. Those guys require help, which takes away from what an OC can do, and puts more pressure on the other OL to win. Then there are the guys who have the physical ability, but haven't quite shown mastery of the technique, and everyone is _hoping_ they can learn the technique and apply it at the next level ... those are usually the guys that bust most often.
Since the job requires soooo much mental work and technique, its sometimes a progression, such as smaller school phenoms like Billy Turner who take several years to become a decent OL ... and by the time they do, they're a FA and not worth the cost. Teams that draft them are simply volunteering to become farm clubs for real franchises in FA. That's why I like the New England approach to OL. Spend little, have lots of turnover, but aim for getting an average to above average OL of limited athletes who can produce immediately. It means you're unit will not be unaffordable to re-sign in FA, and it means you'll be getting satisfactory role player production at all times. Look for durable guys and keep a deep roster of average players with average to above average physical traits, but don't splurge on the phenoms because you'll lose salary cap when they're injured or being developed, and when they become FA's they break your salary cap or leave. Very solid approach, IMHO. Extremely efficient for the salary cap. It allows you to have a decent run game running against pass defenses, and a decent passing game passing against run defenses. If you have a good QB, he can thrive. Tua's mobility should enable us to do that in Miami, and invest big draft picks and salary cap to WR's, DE's, CB's, and other premier positions. While Tua is on his rookie contract, we have a window to excel.
Evaluating OL is tough. IMHO, I'd rather build with Austin Jackson as our LT and add a 2nd rounder or two at RT and C and groom this group to excel. If we can't have a solid to good OL with that investment (1st in Jackon, 2nd in Hunt, 2nd this year for a RT), then we're simply wasting our picks. Kindley was a mid round (4th) pick, and we have 2 FA's one making peanuts (Karras) and one making serious starter money (Flowers), so we've invested a lot already. The time is now for investing in a target for Tua and some defensive cornerstones (edge rusher if one can be found).