AlexB, many thanks! Works great for me, Win2012R2 with dedupe.
FYI, I haven't found any comparable tool yet. However treesize actually shows correct sizes for deduped folders in right side pane (not in left pane actual tree - there it shows the wrong 'on disk' sizes). Unconvenient, but may also work for some, plus treesize seems to be much faster than windirstat.