Yes you make some good points in that with the new rules on reward distribution the value of the cards at the very least will hold value, but more likely appreciate in the long run.
It doesn't hurt to have duplicate cards in this game as there is a very active rental market. Like I commented earlier with olympicdragon, in the past I bought a lot of 1 bcx rewards legends and epics in hopes of one day combine them to max level but in the mean time rent the multiple cards to earn a streaming income. The income I get can reinvest into the game with more card purchases.