Once again, Giseldah has done a tremendous amount of work (some would say it should have been done by the devs) to help us understand the new stat arithmetic. You can see and set your current and potential percentages, as well as the shape of the curves.
https://www.lotro.com/forums/showthread.php?667274-Grey-Mountains-Ratings-Calculator
Use the link in the first post to access it as a Google Doc. (He updates the link when he updates the calculator.)
You can use it online by signing in to Google Docs and making a copy (Under the Google Docs File menu, select Make a copy). You're actually using Google Sheets, their online spreadsheet.
To download it, look under the Google Docs File menu for Download and select the format. I successfully used the OpenDocument version (It opened small, so I had to View | Zoom to 100%.) I was not able to use the Excel version, probably because I still use Excel 2010.
If you have trouble accessing it, let me know.
Don't get too depressed by the results. Mordor had similar magnitude stat inflation and the initial gear and essences, although significantly higher than level 105, were not enough to let us cap things. Over time, higher item level gear rolled out, and much higher essences became available. I expect the devs to follow a similar pattern.