On their own merits, the arena changes are probably good, and should help make arena feel less stale.
I just think it's too little too late. I've already stopped playing Hearthstone, and these arena changes are not really big enough to convince me to give it another try. It feels like Blizzard is trying really hard to avoid adding more depth to the format, because they're afraid of scaring off casual players, but that's going to drive away experienced players, even the casual ones.
Yeah, they really want the casual players, but they picked a game so similar to Magic: The Gathering that its hard to keep it simple without it being boring and stale. I have some hope for arena, but ranked will be boring probably for a very long time, maybe always. The Overwatch team is just much better at making games, and it shows. OW is a way better designed game, and the dev team are much more open with the players, instead of Ben Brode coming out and saying "Oh but these cards are so cool! Its cool man!".