When an event card is presented, you can spend real money to obtain it first that anyone else.
Some time later there is their event, where you can get them for free with the tickets.
And some more time later after that you can craft them, in case you missed them or didn't got all the copies.
I think that they are going to make the new heroes avaliable to obtain at some point in the future, like the event cards.
This was like the "Pre-release" thing. (Or at least I think it that way).
About the OP cards... EA (kinda) knows what it is doing. If a card is pretty OP it will be nerfed at some point in the future (Like they did with Mushroom Grotto).
If a card need buff, it will be buffed at some point in the future (Like they did with Sergeant Strongberry).
The last thing was pretty much a one-time thing. I can agree that the effects of the cards that got changed were pretty op for their cost. Like Briar Rose, that let you kill a Zombot 1000 with a simple 1-cost Sunflower. I don't think they are going to change the rarity of more cards.
