As you mentioned they have patched the game so you can no longer get more than 1,500 points per game. The cool thing is the reviving team can leave once the shooter gets 1,500 and it will count towards his score.
This happens about 3mins into the game and it takes about another min or two to start up another game. So by those numbers from scratch it would take each person 1000 matches to get their level 30 rank and 3000 total matches to get theirs and help the other two people achieve their level 30 achievements.
15,000,000 to level 30
1,500 per 5 min match
1,500 points per match x 3000 matches = 15,000
15,000 / 60 mins = 250 hours for everyone to complete the level 30 rank
Much of this is based off numbers given to me from other people. I really don't know how long it takes to get in a match or if the points always count. Still I know I'm about a 3rd the way there from when I use to play the game legit. Doing it legit alone would take about 500 hours. lol