It only took 8-12 HM EC runs to have BiS (you needed the Black Hole Armouring off Kephess to be viable for you class) and only because of Bracers/Belts. If you ignored those it only took 8 runs to get BiS.
They're doubling that for HM TfB so it will take 16-24 (2-5 months). Hopefully they'll release Nightmare EC around mid-December (SWTOR Anniversary, Dec 20?). So given the decrease in gear I suspect Nightmare TfB won't be out until February or March