Fixing an unintended and unnoticed bug is not a crime. Change my mind.
Entire system was like this from begin. If there is a need, we could think about some ideas for Old cards rather. Like some kind of converting them to New System or selling to NPC. Getting angry about bug fix that was in fact almost giving an abuse (was just missing to actually have "Old Card" in tooltip) surely will not force us to restore a bug. We already keep it like it was for previous zones. So no one is losing anything. We didn't deduct attributes. You weren't lost in anything. To get extra attributes there should be more than minimal effort, because giving attributes for nearly free can cause "attributes inflation", causing every content to be consumed too fast, being bored and not feeling any challenge for becoming stronger.
As mentioned before, rare cards are always supposed to be changed into Unique anyway, so they are not involved into New System more than card sharing between decks. So even Old card is equal to Unique card in terms of attributes. If we missed some rare cards or you think some should be Unique as well for sharing deck, please just kindly tell us instead reacting with aggression.
Greetings