Definitely continue working on the glutes as you mentioned, as this will then feed slack into the high hamstring area. Persistence is key, even if it seems like you’re just smashing the same areas day in day out. As you wrote in your initial post, avoid sitting when possible as it’s death on the hamstrings. If you do have to sit, add in movement (air squats, walking while talking on the phone, etc) when possible. Also, add in banded mobs such as: http://www.youtube.com/watch?v=9rj5YOleets to give a different stimulus.