The only cards that are booster exclusive are in Bronze, Silver, Gold and Imperial Triad booster packs. The Gold ones are going to be your major headache with both WoL and Zidane. I don't recall any card from the Mithril Triad booster that you can't get from other means (trial/raid/dungeon drops or NPC). The later are hard to get, since the NPCs are a real challenge and the drops are stingy as hell. So it's up to decide what's worth doing. I'll leave this handy website: http://ffxivtriad.com/