Hi,
This worked for me - If some of your characters have very low quality portraits when playing with lower video settings, change the video settings to Ultra before using the respec mirror on the Lady Vengeance.
This will change the portraits of your characters to high quality ones.
After this you can switch to lower quality graphics settings.
I only tested with Ultra quality for the Video Settings.
You don't even have to change anything on your character, just use the mirror by clicking on it and then click the Accept button - this will change the portrait of the character if you upgraded the video quality for the graphics before clicking on the mirror.
You besicaly exit the mirror with the quality for your portrait given by the game's graphics quality settings.
