Running, sprint work, etc.
When I started running, my glutes and hamstrings got significantly stronger. They must have gotten visually more pleasing because I got some nice compliments of how I was a flat @ss.
I would definitely recommend mixing up your workouts. Working on the same exercises will only result in a plateau. Perhaps that is what you have hit. Stiff leg deadlifts have me an incredible workout for my hamstrings.
I found this site which may help: Hamstring Exercises
My work computer limits me to an extent but give it a try.