SYMPTOM:
Where there are too many elements in the Visual Insight graph, data label will be overlapped. For example:

CAUSE:
This is a known issue with Visual Insight pie chart graph type in Strategy Web 9.x.
ACTION:
It was tested that in Strategy 10.x Visual Insight, which supports HTML5, data labels will not overlap each other. Some of them will be dropped if there is not enough space. Please upgrade to take advantage of this enhancement.
WORKAROUND:
Use a different graph type on Visual Insight or use regular Strategy report instead