Yeah, their only real extra utility is mind flaying to keep melee on a target/slowing the EFC, which really only outweighs the added damage, healing and mana efficiency from holy/disc in a very good team environment. IMO, if you've ever played a shadow priest above level 20, it just feels completely gimped and naked at this level. It doesn't really get any of its spec-defining spells/tools until a bit later on.
It is easy to respec though, so I would definitely recommend trying it out for yourself if you're interested. If you have fun and feel like you're doing well, good for you! If not, try out disc and/or holy and enjoy being super awesome.