It will be nice to have some charting possibilities in designer.
I'm working in economical newspapers, and we rely on illustrator due the huge amount of charts we need to do.
Our basic workflow is:
Excel, OpenOffice or Google Tabs -> export data to CVS or just copy paste -> illustrator
or using some web tools like http://rawgraphs.io/ to generate svg and then back to illustrator for finishing touches.
Sometimes we use D3.js (https://d3js.org/) to generate our custom charts to svg and then jump to illustrator again.
I think using some library like D3 could be the way.
It would be great argument for us to switch to Designer if we can do some better charts than in illustrator.