I've never had DPI-related export issues with artrage, one thing I have noticed however is line art layers in AR look and act weird when exported between different applications through .psd file export.

I don't remember if it was .psd to artrage import or the other way around, but lineart that is created as a transparent layer with black strokes of varying opacity always looks darker and muddier when exported back into photoshop.

the solution here, if your workflow allows that, is to create a layer underneath the lines, fill it with white, merge the lines down on it, and set the lineart layer mode to "multiply" - it will export 1:1 as seen on screen in artrage.

I used to suffer with this in the past as I rely on lineart a lot, and do all my color work in artrage, and both digital pencils and scanned pencil lines have this problem when taken to a different app for finishing and other stuff like blending and effects. it is frustrating, but can be resolved.

I haven't found any in-app options to prevent that issue though, and it is consistent across artrage 4, 5, and 6, and I don't own vitae yet, so I can't comment on that one.