if your criteria is JUST DF, then you could do up to and through the extreme mode primals, just dont expect much success. Coil of Bahamut is not available through the DF, but you might be able to snag a group through the party finder, same with the extreme modes. Coil turns 1-5 will be available through the DF in 2.2 I believe and will be nerfed a bit, to make way for turns 6-9

reliable success through the DF? HM primals up to garuda, and crystal tower.