The dashed line is wrong when using data.groups and data.regions togather

        var chart = c3.generate({

            data: {

                type: "area",

                groups: [['data1', 'data2']],

                columns: [

                    ['data1', 30, 200, 60, 400, 150, 250],

                    ['data2', 50, 20, 50, 40, 15, 25]

                ],

                regions: {

                    'data1': [{'start':1, 'end':2, 'style':'dashed'},{'start':3}], // currently 'dashed' style only

                      'data2': [{'end':3}]

                }

            }

        });

http://jsfiddle.net/7ydhyjm3/2/