Is this chronic shoulder pain or simply bike related? Mine is chronic - not overwhelming, but live with it. Injured somehow - over time have forgotten the specific event. Gave up golf, but when feeling better went to driving range. Big mistake. On the bike, had to explain that was not giving wierd hand signals - just stretching and extending my right arm as tightens up with the limited range of positions even on a road bike handlebar. Don't have a carbon handlebar which MAY have an impact on vibration, but that is not the problem. It definately WILL NOT provide more positions.
That gets back to the initial issue. Is it a fit problem...or a welcoming to aging and a new friend, arthritis.