Can you please tell me, using the numbers displayed next to the legend items in my picture, what exactly the order should be?
If the wrong legend sorting is only happening in your attached qvw document (which wasn't clear from your OP), then simply press the Chart Properties->Presentation->Settings... button (in Legend group) and enable checkbox "Reverse Order".
In both the attached document and the picture I expanded with numbers, the sort order of the legend is identical to the sort order of the stacked bars (give or take a "Reverse Order" checkmark). So my conclusion is that in your document, you want both sorted according to the number sequence from the CUR_WF_SORT_ORDER Excel sheet?
In that case, open Chart Properties->Sort, select "Workflow Step" from the list and in the Expression sort field, enter CUR_WF_SORT_ORDER. You'll get something like this (smallest number first).
BTW if you want to invert the sorting order, select "Descending" in the Expression sort order listbox.