they added a few classic cards to replace the class cards that were sent to the hall of fame. we're getting another round of them before the next expansion. they're pretty simple. you can read more about them here:
https://playhearthstone.com/en-us/blog/22483774/ . they're weak cards that give the class some flavor so new players know what the class is about.
there have been a few ladder changes but i don't remember the exact timeline of it so i'm not sure what you missed. the biggest change was making it so you only lose 4 ranks when the ladder resets at the beginning of the month. they also added ranks 26-50 so new players are sequestered with other new players for a long time before they start hitting players at rank 25 who have complete meta decks. they also get pack rewards for hitting rank milestones. there was also a minor rebalancing to the number of stars per rank. it went to 5 stars per rank at all ranks back down to fewer stars for lower ranks.