Since it is actually translating to get you a DWG/DXF file it will almost always use splines / polylines for parts that are not straight lines or constant arcs/circles. I solve this by opening in Autocad and putting in proper tangent arcs and/or circles, but it almost always happens. I am not fimular with Coreldraw, but if you can create arcs and lines in it then you can manually fix it in there as well.
In the dxf export settings you can specify splines conversion as splines or polylines. Some burning software has a smoothing options that allows to clean up polylines or splines with many points. Another option is to open the dxf in autocad and retrace manually or use a lisp function
google PLDIET.lsp for the lisp
I found the solution, but I have no clue why it works as a solution. If instead of generating the DXF from a .drw, I put together the sheet as a .sldasm and then save it as a .Sldprt, and then open that and save it as DXF, all the lines come out uniform. No clue how this changes the DXF interpretation of parabolas (there are other splines that it has no problem with, like the outside of the airfoils, so it's clearly just the parabolic features that are the problem) but it works