The man is absolutely going top15 if not top10.
Every year is different. No top 15 teams last year needed OL help. That's why Decastro fell that far. This year is different. Arizona, Carolina (us), Tennessee, St. Louis, Cleveland, and Buffalo all needs OL help and could use a Warmack.
I hate to say it but big college programs play a huge role in who get drafted, and early or not. Scouts and experts loves these Bama players bc of Saban, the experience playing in a pro system, and the leadership attitude these guys have.
First, the notion that no team in the top fifteen (a list including all of the teams you listed except Tennessee) needed any offensive line help is ludicrous. Second, DeCastro didn't just fall out of the top fifteeen. He fell all the way to 24. All of the teams that you listed passed on the next great guard last season, and they did so because they don't value guard play as much as they value the chance to get a player at another position. They will do it again.
And DeCastro checks all of those boxes, by the way. Played in a pro-style offense under Jim Harbaugh, was a unanimous first-team All-American, a leader in the program. He didn't get picked as highly as he was graded because he plays guard.