This probably won't be helpful at all, but this might give you some hope. Last year my hamstrings were pretty tight, even after my dance class. (I'm a beginner, so the class isn't particularly intense.) I had taken a break from ballet for my last semester of college and eventually started exercising (i.e kickboxing, etc.) mid-summer. I was surprised to find that my hamstrings weren't tight anymore before and after I did my workouts. I'm not exactly sure what this means... maybe the muscles just have to be REALLY warm in order not to be tight. Maybe someone else will have some better insight on tight hamstrings.