There's three kinds of "artifact" armor. There's the ilvl 50-55 set you acquire over your level 45 and 50 job quests, there's the item level 90 set that WAS acquired with tomestones, but is now acquired via the antiquated armor that drops in certain dungeons (I know Sastasha Hard is one of them, there's another that's the same difficulty that drops it as well), and finally there's the item level 200 set that was acquired using tomestones, but is now acquired via Centurio seals.