16 hours a day, every day, with a 90%+ win ratio against Horde premades in battlegrounds, for 6 weeks from rank 10 to rank 14 for me. That is well over 2000 games played. Not including the months it took to get from Rank 1 to Rank 10 solo before getting a team.
Seeing people with the new Grand Marshal and not even the 150 rated battleground wins achievement makes me a bit sad.