I did fail to mention this in the first reply, but the times I've seen people having hamstring issues they were almost always related to a previous injury. Instead of checking fit or any measurement on your bike or body, I'd check to see if there is a noticeable difference in flexibility between the two legs.
I personally have calf and hamstring issues on my right leg, and it's not a coincidence that it's the leg that I have injured previously - and the flexibility is severely compromised in comparison to my left leg as well. My right leg is also shorter than my left and my right foot also collapses considerably more than my left at the bottom of my pedal stroke as well. All these factors coupled with some climbing and I do get a burn sensation in my hamstring and it is extremely tense at those moments as well. Some foam rolling and regular stretching got this symptom to go away after about a month of consistent daily stretching.