I think only OV and Dub are necessary since all films/dramas around the world use ODub (because that is the normal practise).
I would suggest adding it like Chinese sites do instead of using tags, because in tags there's no way to say *which* actors are dubbed. So for most dramas you'd be using both tags since some are OV some are not.
Such as here with Sun Li in Empresses of the Palace - the last line lists "Dub: [the two actresses that dubbed her]". Maybe in Cast listings, contributors can add [Dubbed] after a cast member, unless people really want to also be listing dubbing actors on this site as well.