If I understand the mechanics correctly, the Tarot Cards improve the general chance of getting items with tier Relic and above, which is...hmm, 10%. The "Hardcore" tag for a Void Crusade, however, improves the loot from the Void Chests at the end of the Crusade. Given the proper strategy, there're 7 keys to open those chests.

In summary, the trade is reasonable.