First of all a NT is not supposed to be 6-5. They should be under 6-3 because if you are that tall (6-4 or over) then you can't get good leverage. And also Robertson is 6-1, 315-320, meaning he would have a bigger width than both Okam and Shirley. Okam would however be a great 3-4 DE to look at in the first round.
Ted Washington is 6'5"....He's the prototype....Granted he's now about 50 Lbs heavier than those two, but 320 out of college, is over 335 in a year or two.... Height doesnt matter, and more of it is generally better. If the guy gets stood up, then his wingspan comes into play....(though obviously you arent looking for that regularly....) The only real question is the ability to command and dominate double teams. Apparently the book on both of those guys is that they meet that requirement....
Vince Wilfork - 6'2" Pat Williams - 6'3" Casey Hampton - 6'1" Sam Adams - 6'3" Jamal Williams - 6'2" Jason Ferguson - 6'3" Aubrayo Franklin - 6'1" Kelly Gregg - 6'0" These are the best NTs in the league, all under 6'5". Yes I know Washington is 6'5" but he is also 20-25 pounds heavier than the heavest player on this list. It is easier for smaller, wider more stout guys to command double teams because they are so wide. If you are tall and the same weight as the guys on this list (in Okam and Shirleys cases even smaller) you are going to be much slimmer and you wont be able to get leverage and to hold your ground. Remember you are going up against centers and guards who are not 6'6" or more, like tackles are, you need to be shorter and wider than them to get the leverage and push you need.
We need a guy who is 6 2 315-320 with a wide body. That way he can put on 20 or 30 pounds and still have the mobility to get around. Wilfork and Hampton were both a lot smaller coming out of college but both have huge wide bodies so they were able to add weight without giving up speed. You really need a shorter wider leverage player who if blocked one on one will blow up the play. That way he forces the double team and one of the linebackers is left unblocked.
It still just kills me that Bradway traded the farm for Drob and Wilfork lands in the Pats laps the following year..... Man, it just seems like they caught every break and we can't catch just One.
That's not failing to catch a break, it's shooting ourselves in the foot with a trade-up and then complaining that we're limping.