I've never liked DoTs. I would rather do one spell that does it's full damage rather than use another spell that takes 6 more spells in total time to do it's full potency even if it's slightly stronger than the spell that does it's full damage. I think not having a DoT adds to RDMs simplicity which was SE's intent for the job. I don't think it'll ever have a DoT and honestly I wouldn't want it to. Matter of fact I would probably flat out refuse to use it.