I Have no doubt that they Do. Now does EVERY SINGLE ONE smoke pot ? Of course not. But I got a few Points here:
1.) Looks at 90% of the Players in the NFL backround/Where they come from. Selling, let alone smoking was a Way of life and Surviving for alot
2.) As you already Stated, NFL is starting to Loosen the rules
3.) These men spend almost 10-11 months out of the Year pushing their Bodies past its limits , and for 4 months every Sunday have to run full speed at another humans, using their head to bash the other humans skull. Shit hurts
4.) Its becoming State legal in more places and it works to become Federally Legal, Which means alot of people smoke dope

Even before the new rules lightening up, players still knew when they would be tested, and could almost always be prepared to be clean. If you listen to ThePatMcAfeeShow , you hear him talk about it every day . Other players and vets , its just common . Yeah I think like 85-90% of the League Smokes , just know the month and weeks not to , so they are clear for testing . And that will probably only grow as the League loosens up the regulations more and more