Alright, lets get into this. I'm coming from a competitive TCG perspective on this only and I havn't been keeping up with Hearthstone all that much so i'll be comparing and contrasting the changes with what I know about the genre as a whole and the tempo storm meta report.
As expected, unforced change in a rotation. Nothing to see here.
Too versatile? It draws a card and sacrifices its vanilla stats as a result of that. As of today 3 of the 5 tier one decks run 1 copy each. It is a good card, nothing more. It's not an auto include and it's certainly not too versatile else you'd be maxing out your copies in all 5 decks.
Now this is an overpowered card. Its effect immediately limits design and forces the team to think about "what's the impact on the player if their opponent now drops Sylvana?" and they're being clear about future plans and scope.
Blizzard, nobody is playing 8 mana minions because your entire meta is forced into playing smaller aggressive minions and the only way to counter it is either 1. Be aggressive yourself or 2. Recover your entire life total. Your lack of efficient off-turn (or even on-turn for that matter) interactivity forces people to play in this manner. Unnecessary ban, if your complaint is "well there's nothing better" then make something better or on par, balance it, but make good cards that are worthy of choosing.
Although these could have their place in standard these are reasonable bans for the reason i'm about to describe.
Blizzard is clearly trying to pull off what Wizards of the Coast have done a couple of times in the past, a power slump. In a world of many mediocre cards and few good cards the same cards see play over and over again so it's easier for the balance team to ban, change or rotate the cards people enjoy playing with to try and balance the field for large upcoming releases. The solution is effective but, has it's downside in the fact that people are so used to the previous power level that the new meta becomes unexciting and dull. There are no big swings anymore because there isn't any cards that can do that, we will see more variety in deck lists but how much more? Shaman is still as powerful as ever, hunter is still an incredibly aggressive class and even if Patches sees a nerf the only card that could heal you past aggro strats is now gone with rotation...
Anyway, lets continue.
FINALLY! The way it should have been the entire time. A solid amount of cards for the year to give the meta opportunities to change and adjust. This is a huge change that could be a far more beneficial change to hearthstone than anything mentioned above.
Copying Pokemon TCG Online. Good move, keeps players incentivised and morale stays higher in constrained metas. The problem with this? "will be available for a limited time"... ffs.
Blizzard have made the right move with the wrong justifications. Well, they're the right justifications but only because we're far too deep into the game's cycle to do anything about these core cards that have been made from day 1. Lets not forget that Wizards and Konami made the same mistakes with their respective games in the early days and tried to do something about it. Both made mistakes and both made exceptional design choices, Blizzard have yet to do the latter. Blizzard have nearly no time to rectify this, prize pools are dwindling and the competitive scene is dying from what i've seen. This year is absolute make or break for Hearthstone, God help it if its Twitch numbers go down.
What should Blizzard actually do?
I sit here and warrior over Hearthstone frequently. The game captured me in it early form and I watched as it was quickly destroyed by a stubborn and obstructive design philosphy despite it sitting in a completely different space to anything else i'd seen before at this level.
So what do I think they should do? I should at least give a solution to try and fix what is broken. In my opinion it's the lack of substantial off-turn interactivity. In Hearthstone the only two things that can interact with an opponent on their turn are on board effects and the big one, secrets. Secrets are vey much like traps in Yugioh and can be effective when balanced correctly. We all saw what happened with Paladin secret decks when they took one class too far, but it doesn't have to be like that. If every class had 3 effective secrets they could dip into that were themed around the class capabilties then the playing field could become a lot more balanced. Blizzard still need to take into account card costing, effect strength, deck limitations (not too much interactivity else we might end up in fatigue too often) and ways to push through set secrets (again for each class) but that's their job, not mine. Finally, 30 cards is just flat out not enough. Give players a way to cycle cards back into their deck from the grave, if players have to balance between an on board tactic and not moving into fatigue then combo archetypes might actually come about. This would also give a neat solution to get around set spells and RNG cast spells that we've seen so often in the past.
If I think of anymore solutions i'll post again in this thread.