If you played this game in the past and wanted to return, then don't. It's unplayable for returning player. Everything changed. OP cards everywhere. Your old cards are obsolete now.
This game is an example of "The Computer Is a Cheating *". There is no "AI" at all, the enemy just have its entire deck in hand and use the best one however it wants.
F2P, played for 2 weeks. I hit a wall at league 9. I can keep winning and losing equally even with 4 legendaries (Tengu included). Most of the time I lose to those Groot, Ghosta, Santa, etc...
Free player, 10th day: 2 Legends and 12 Epics. It's P2W, sure, but those who complain before even reaching L15 or L10 are used to easy game where everything just get handled to them.