I don't know if everyone is now aware about this so that is why this post is here.
Yesterday some of RGW incl myself noticed that dbm wasn't working, that really became a problem with the Ultraxion fight.
At that point someone gave us the hint that they split up the addon and that you had to download the Cata version by your self.
So for those that are using DBM and still havn't done this, then go and download it here (http://www.curse.com/addons/wow/deadly-boss-mods-cataclysm-mods)
Make sure after it is installed to load it, as some people had to load it manually.
yes, a lot of RGT were made aware of this issue as both myself and milly were talking about it last week.
As you have pointed out, the cataclysm part of the add-on is now in a sub folder(the same as Wrath, BC & Vanilla) so this requires you to download the add-on + the other packs if you venturing into the dungeons of that era.
As the "new" part of wow will be Mists, so now the current cataclysm part has been demoted to "old content"... even though we are still in cata.. hmm, blame the writers of DBM, for this.