When you have a dataLabels displayed on bars/columns that are all low value and close to one another, the dataLabels become merged and unreadable.

I added some code in the alignDataLabel function that hides the dataLabel if it cannot fit inside the column/bar it is to be displayed in. When the column/bar size changes by either resizing the window or by turning off some series the dataLabel becomes visible, or invisible if made smaller.

Here is a gallery demonstrating the changes: http://imgur.com/a/Qn6ui

The changes are simply adding the following code to the alignDataLabel function:

    if ((point.series.options.stacking != null && point.series.options.type == "column") && (alignTo.height + 10 < dataLabel.height)) {
        dataLabel.hide();
    }
    else if ((point.series.options.stacking != null && point.series.options.type == "bar") && (alignTo.width < dataLabel.width)) {
        dataLabel.hide();
    }