Hi Stefan,
I have a very intriguing solution 
You can use
var oModel = new sap.ui.model.json.JSONModel({
businessData: [{
name: "Foobar ",//just add an extra space.
id: "id01",
value: 100
}, {
name: "Foobar",
id: "id02",
value: 200
}]
});
The library will remove the space from "Foobar " and display "Foobar". Its a very funny thing about the viz chart library.
Another solution, where you would have to load the entire viz library independently with a different namespace and disable the replacement of the multiple similar dimension values into one single value(You would just have to comment some lines of code). But this is a pain.
Hope that works for you 
Regards,
Naren L Naik