We understand that some people will not like the change, and you are certainly free to sell your cards whenever you would like. The fact of the matter is that the amount of rewards being given out compared to the amount/value of cards required to obtain them was unsustainable and needed to be fixed.
Your case is actually a good example. Your cards are mostly silver or at most gold level, yet you are able to get to Champion I with no problem. Also, from a strict ROI perspective, the amount of rewards you can earn at Champion league compared to the value of your collection is off the charts.
Our focus and goal is on creating a sustainable game economy that can support exponential growth over the long term. The players who got in early, like yourself, have had a big advantage in being able to earn extremely high levels of rewards compared to collection size for a long time.
RE: New Reward Cards & Collection Power Update