I have a look at the source code.
aggregations: {
'items': {
multiple: true,
type: 'sap.suite.ui.microchart.HarveyBallMicroChartItem'
}
}
this means that the control expects many items.
But in the renderer, it just render the first item. So you will only see one item. Unfortunately...
And you should use
sap.suite.ui.microchart.HarveyBallMicroChartItem
and not
sap.suite.ui.commons.HarveyBallMicroChartItem
Thanks
-D