It is a nice surprise when a card drops from battle content but I think all cards should be obtainable through playing cards and MGP. The ones that can currently only be obtained through battle should be added to TT NPCs as an alternative way to acquire them. In particular the primal cards such as Ravana and King Mog have almost no chance to drop in hard modes, so they are mainly found by hardcore players farming extreme difficulty. The people getting them are not necessarily the same people who actually play TT.