I think that you have a clear cut # 1 wr in AJ this year, that is the easy part here. Then you have that second tier of players of:
If you want to draft of pure potential and skill I'd say that Fitz and Calvin would be 2 and 3, but they have some question marks along with them and there team. I would downgrade them both slightly, very slightly. I may even keep Moss as the # 2 wr because he is playing for his last contract, so the $$$ is going to be a big motivator. With Wayne you know what you will get, 1200 yards and 10 + tds.
The next tier to me consists of:
You have, IMO, one consistent player here, Colston. He is on a high powered offense and will get his 1000 yards and 10tds. All of these other wr's have some issues and could end up much higher or much lower at the end of the season.
DJax- is Kolb the real deal? Will he drop off with the qb / rb change?
White-if the running game stays consistent and Ryan improves he could have a huge year
Marshall- new offense, new qb, now is on a run first team
Jennings- had a ok year last year, will he rebound, he has a elite qb to work with
Austin-will he match last year, will Dez hurt his numbers, can Romo stay upright to get him the ball
S.Smith-new qb, no other receiving threat on the team, broken arm so he will miss most of camp
S. Rice- had a huge breakout year, can he do it 2yrs in a row, what if Favre doesn't return?
To me I'm ranking my players, sticking to my rankings and see who slips to you at the end of the first round and not reach for any players too early with the thought of having to take a wr your first 2 picks. You may even be able to go skip wr in the first rd and get a solid option such at Colston in the 3rd /4th pick. There are too many players that scare me that haven't done it, but have potential, I'll always take a team of Wayne, Colston, etc, the proven players that put up the stats each year. Good luck.