Hog Rider: Not all that surprising. I haven't used the card in quite some time so it doesn't impact me. I know most people were saying this card was OP, but for me it was one of the easiest cards to counter.
Prince: The Prince was starting to creep its way back into the Legendary meta with the most recent update, and I fully expect it to make a return. With the PEKKA buff, I suspect we may see a return of the double Prince/PEKKA combo.
Goblin Barrel: I honestly don't think I have seen this card since Arena 3/4 and I doubt that will change. I thought about trying it out with my Miner deck, but there are just better cards to use. That likely will not change.
PEKKA: I am a die hard PEKKA fan and this change makes me happy. I was using PEKKA until the most recent update and I actually did not think it was that bad. I will probably go back to my old PEKKA deck when the update hits.
XBow/Mortar: You're kidding me, right? This is quite the timely buff with the most recent emote blog post. Expect salt levels to go through the roof. I'm calling it now; people are going to use some combo of Royal Giant/Mortar/Xbow and it is going to be absolutely obnoxious.
Furnace: I think I've seen this card played about 5 times since it came out. I don't see that changing. The only way this card becomes useful is if it spits out Fire Spirits at a slightly faster rate.
Guards: Similiar to Furnace, I think I've seen this card all of 5 times since they came out. This is a positive change, but I don't think they will be used much still. Though, at only 3 elixir I could see more testing with them happening.
Witch: With the last update, this has a 27% damage increase now. The problem with this card is, where does it really fit in? They mention taking down Minions faster, but the Musketeer does the same thing at a cheaper cost.
Lava Hound: No longer can be laughed at. Granted, the buff isn't as much as people think it will be at 28%. My level 2 does 29 damage per second, so we're talking an increase to around 37. That isn't going to take a tower down, but it will warrant more attention.
Cannon/Tesla: Poor cannon. With the Tesla increase I think it may have finally reached the breaking point of people making the switch. Everyone used cannon because of Hog Rider, which is why it is laughable Supercell always said "it is used too much".
Most disappointing: No Royal Giant nerf. I'm shocked there was no mention of Royal Giant. People complain about Hog Rider, but Royal Giant is way worse. It would be a miracle if I went more than 3 games in a row without someone using the card.