Oxygen core pots and the potting mix you used are better suited for Orchids, not Dracaenas. While it is true that Dracaenas don't like to be overwatered, unlike Orchids they are not epiphytes and they do need to have moist soil around their roots.
If you indeed left most of the original rootball intact, then you should be able to undo the repotting that you did without disturbing the roots much more. Do your best to gently remove the potting mix you added and put the Dracaena back into its original pot or one of similar size. If there are any spaces that need to be filled with soil, use a standard potting mix.