Right picture: instead of being properly transparent, the areas between the Arc's jewelry is covered with a dark red color. The affected polygons' transparency varies throughout the character's idle animation, as though the angle you look at the Arc changes its transparency.
Left picture: Rarely, after a respawn (most easily reconstructed via hero swapping in Demo mode), the bug will change to the hair piece (Magnificent Flame) casting an erroneous shadow on the charater's face: Notice the shadow-free block right above her eyebrow.

This bug only occurs with the portrait version of the Arc. It does not occur when viewing the character in the menus or on the game field.

I've verified my game files and made sure there isn't a mod or launch option interfering. Tested with DX9 and DX11. Bug is a couple years old at this point I think, but I thought it might be worth bringing up again during the current call to action regarding bug reports.