A diverter can be added, but it has been my experience that they can and usually do create problems. The problem is water wants to flow downhill in a positive manner and when a diverter is added you are sending water across the path it wants to flow.
Diverters trap debris, leaves, shingle granules and are usually forgotten and not maintained. A water dam is created and hydraulic water action can develop, sending water up and under your roof system. A gutter under the roof edge, would be a better solution if possible.