I agree with nerfing Argent Braggart, but that's about it.
Guardian Animals can't be nerfed, it's also a hunter card and it's not a problem there at all. If this needs nerfed I think the target is Twilight Runner. I think Overgrowth would be a really lame card at 5 mana too. Barely better than Nourish at that point. Solarion Prime is strong but requires a ton of investment. I think the mage spell pool in general is a bigger problem, and Solarion Prime is another card that would just be kinda limp at 4 cards.
The Blastmaster Boom nerf is lame. That's really arbitrary. While it's a powerful card, I'd probably hit bomb warrior somewhere else. The wrenchcalibur nerf is a little more sensible I think, though that makes the card pretty weak in anything that's not strictly bomb warrior. The Demon Hunter nerfs seem totally unnecessary to me. So does Greyheart Sage. You could probably nerf it's stats a little. (2/3? 3/2?) But I think increasing it's cost really kills the card.
Shaman buffs might be okay, I think buffing Tidal Wave would be a huge mistake. But the Nithogg buff seems all right to me. The main problem with that is the card is cycling in six months, so I dunno if it's worth it. Vashj is fine.
Also yeah I'd like them to just kill Tortollan mage. I'm really not a fan of those sort of degenerative combo decks that just grind you out. There either needs to be more counterplay besides crummy tech cards, or they need to kill the deck.
I'm surprised it's only really Braggart you agree with seeing as Paladin is less powerful than the other decks targeted, if that was the only nerf paladin would struggle more if other decks left the same. I obviously do think Braggart does need a slight nerf though.
Druid is oppressive right now when it draws well, which is often. Fair point on GA being a hunter card though hadn't considered that. I do think it's the ramp that needs targeting and it can't be Wild Growth. Using Wild growth as an example though, if 3 mana is worth 1 mana ramp overgrowth is obviously under costed at 4 mana. I think 5 mana is very reasonable in that case.
As mentioned looking at HSreplay at some bomb warrior decks, Blastmaster Boom literally has a 77%+ played win rate, that's insane I don't think I've seen anything as high nor can I find any looking now. Seems like a pretty obvious nerf candidate to target bomb warrior.
I don't think Tidal Wave will ever see serious play at 8 mana.
Argent Braggart is just the only nerf I agree with because it's a really simple nerf that nerfs a very excessively powerful card but keeps it very playable. I think there're other nerfs in classes that could happen, just don't agree with your specific nerf proposals.
Overgrowth at 5 mana is just so underwhelming and it's such a lynchpin card for Marsh Hydra, Bogbeam, etc. Even if it's too strong at 4. I think if there's an issue with druid, it might be the critical mass of ramp (Breath of Dreams, Wild Growth, Overgrowth), but without Overgrowth I think that deck (which isn't that strong) is pretty horrible. I think the bigger issue I have with ramp druid is how excessive it is at the top end, but I really don't know how to nerf those cards
If you nerf Bomb warrior overall you nerf Blastmaster Boom. Blastmaster Boom is entirely dependent on the deck's ability to put bombs into your opponent's deck. You nerf bombs, you nerf boom. But I'm not sure what form that should take. I think changing Wrenchcalibur to be BC/DR makes a lot of sense but that might be too hard a hit on the deck.