Sorry to say this - but what doesn't want go into my mind is that somebody give me a gift but want later bring me to pay for this gift - than it is no gift at all.
Or call it a reward - how it is possible to give out a reward and ask afterwards for additional payment for this reward ?

I mean I want have this cards to play, so in general I am fine if they are soulbound as I can play with them and this is what I want, BUT: I don't want receive than hundreds of additional copies from this card without any usecase before I don't pay for this cards - this is what I understand, than they should allow me to exchange this useless reward cards above max-level at least in some other soulbound stuff like merrits, potions, dec-b, maybe even power-core for land or whatever.
Or revive the mystery potions again and let me exchange them against mystery potions - I liked this moment very much when you open this potion and luck if you get something great and if not at least you got a small reward who was really a reward.