AFAIK, they're all pretty much in the same area potency-wise. Also, I think the potency relations are pretty close to their respective 2C-x analogues, ie DOC is to DOI what 2C-C is to 2C-I etc. Going by that, DOC is somewhat less potent than DOI (which is actually the case if I'm not mistaken), DOM is less potent than most other DOx (as is the case with 2C-D in the 2C family), etc. Someone correct me if I'm wrong.