Concerning First Defender
Wrong. This isn’t new design space. You easily could have designed this card in the old rules with assigning damage

First Defender (In combat, Lethal damage must be assigned to ~ before it can be assigned to other creatures blocking or blocked with ~)

They could probably word it better, but it can easily be done. Also, I will agree that changing blocking order isn’t interesting design space. Most of the time, those spells will just be dead cards, since double blocking doesn’t come up that often, and when it does, it will almost always be worse than just packing removal.