I had a Lightforged priest that I played as Disc back when it was basically Smite spec. I had both healer and dps selected as roles, and ended up in a BG as Shadow. I just couldn’t do a Lightforged Shadow Priest and scrapped the character.
This is ironic when you consider my velf priest (the LFD’s replacement) I usually play as Disc, and actually leveled her as Holy because it was easier to do dungeons as.