It may be a glitch, but one of my rep toons has been killing bormu and it's being counted towards the achievement

The dark side eye colour is the same as " dark side corruption makes you ugly" - it's just a game thing. I agree that both are silly. In Episode III, Anakin's / Vader's eyes changed colour outside the Jedi Temple and then went back to their normal colour; the Emperor's features became ugly as a result of the force lightning bouncing back at him. In Episode VI when Vader's mask is removed, all we see are scars from his duel with Kenobi, nothing more.

I do think the armors could use a bit of variety. My Sage is wearing trousers and a tunic because I couldn't stand the "skirt" which to me looks more ceremonial/off duty garb.