You can create a 2 dimensional array out of the 2 arrays you mentioned and use the "DataLayout" and "DataOrientation" attributess for the new array you generated. Please have a look at the attached sequence file created using TestStand 2010 version to know how it can be done. I have tested the graphs in XML reports.
I've tried with this sample with TS2014, it works well.
but i don't know why i get 2 seperate curve in TS2013, attached the graph and the seq file. please help to check again. thank you very much!