Portraits are always regenerated when using the respec mirror (if you confirm rather than cancel). Try increasing the game resolution and graphics settings as much as possible (performance isn't really an issue, as long as the game will respond to input), use the respec mirror again and see if that helps with the quality of the portrait, then restore the original settings. The level for character creation is different than the respec mirror, so I think the lighting would be slightly different, as well.
Ah, so there is currently no way to maintain the special Origin portraits while only changing attributes and other characteristics? Also, the change does happen even after hitting Cancel without changing anything.
