Percent of Total (rows/columns) FOR OLAP CUBES
Percent of Total (rows/columns) is still needed FOR OLAP CUBES.
Excel has no trouble with this.
But Power BI still cannot express values from OLAP cubes as percentages of the row or column total, forcing users to either go to Excel, or else go back to their admins and put these calculations into the cubes themselves (nullifying the self-service advantage of Power BI and causing administrators to curse under their breath :-)).
MA Roberts commented
I would add: also a "Percent of Grand Total", just as you can do in Excel. It is just so painful that this isn't part of the table / matrix functions for a Cube - things that Excel does simply and elegantly that are a royal pain to accomplish in Power BI.