I am now going to give my (unqualified) opinion on all of these changes.
Wall of text, incoming!
Neutral
Spark: Seems like a good change I guess. Spark isn’t that strong, I don’t think this will break the game.
Fruit Ninja: Hmmm I’m not sure about this one. I think having so much potential attack is dangerous. I think making it a 3/2 with no frenzy is maybe fine?
Star-Crossed Starlet: This change seems kinda bonkers. Finesse is already strong, and Starlet is already a good card in a virtuoso deck. I think she’s fine at 3/2, just make the ability optional.
Troq: More text on Neutral cards: ehhhh. Troq buffs: good I guess. I don’t think Troq is the reason bashing is bad.
The Boot: I kind of like this actually. Could prove to be too strong, maybe, but it’s interesting and cool.
Red
Scorch: Might be too good? Red starter already has a lot of ways to split damage around, and one of the interesting things about it is getting around its targeting restrictions to achieve your goals. Allowing them to just kill any damaged hero for 3 gold is… really good.
Zane: This is cool. I’m into it.
Detonate: Hmmm could prove to be degenerate, would need testing to see.
Pirate Gunship: Now this is the change we’re all after. We could even nerf it more, I think, but this is a very good start.
Rickety Mine: This makes the mine always net positive 1 gold, and sometimes it goes into insane gold amounts. Probably makes this quite a viable card, although @Toan might disagree (“it’s already perfectly viable, you just don’t know how to play Red”)
Crashbarrow: I don’t actually think Crashbarrow is too strong. Disagree with this change.
Jaina Spells: Hoo boy. When we said “Buff Fire” I don’t know if this is what we wanted. This could be super insane, but it’s really hard to say without playing it. I’m reserving judgment for now.
Green
Ironbark Treant: Seems… fine. I think Treant is already “good” but now I guess it’s “still good”. Not fussed either way.
Rich Earth: Yeah no. While I was at work I came up with a totally not balanced but intended to induce thought version of this card: “3 gold. Your workers are free. 
: Summon a 0/1 green Wisp Token.”
Maybe it can have Haste too, I don’t know. Now, iterate!
Midori: Yeah this change is good. We all agree nerfing Midori was necessary, and I think we all agree it was nerfed a little too hard just to make sure it was not ever going to be a problem. I think we can confidently bring it up a notch, and allow synergy with Calamandra.
Circle of Life: I’m really kind of meh on this? It could prove to be really strong, I haven’t thought through all the implications. Probably going to need a whole thread to discuss the potential of this, so I won’t bother trying here.
Gemscout Owl: Yeah seems fine. Although, note that not every spec should have good air defence. There’s a reason you get three.
Chameleon: I guess? No-one plays this anyway, so it’s probably good.
Predator Tiger: I don’t know what the rationale for this change is, but I’m a little concerned about it making it too easy to snowball early with Calamandra. That’s a big unit to have turn 3.
Giant Panda: Seems good.
MoLaC: I like the idea of reducing the buff, since 5/5 is just so oppressive that this card is super feast or famine. If we reduce it to 2/2 though, I think I’d make it require only 4 counters. Still super strong, but not game-breakingly so, or at least I hope not. Could be wrong. And the healing is nice, because it helps you keep attackers alive for more attacks!
Blooming Ancient: I’m not sure how much this will actually help, and it reeks of bandaid. Would have to test it to see if it’s actually a good enough nerf.
Oversized Rhinoceros: I think this card is at a good power level already, I think we just need to nerf the stuff around it.
Black
Deteriorate: I think we all agree this is a good change.
Thieving Imp: See above.
Vandy: Yes, obviously.
Dark Pact: I don’t like this. I agree the current drawback is too small, but I think Dark Pact is really cool, and I don’t want to see it become niche. I think maybe just increasing the base damage to 4? Or dealing 1 damage to Vandy I could maybe get behind. 2 damage just feels excessive.
Metamorphosis: This seems fine I think, but does reduce its power a lot. A different thought I had was it keeps all its current benefits but can only be cast on one hero per use. Not sure if it should still sacrifice all your units in that case, but maybe.
Banefire Golem: I’ve never seen this card played, so this is probably a good buff.
Garth: Reducing the draw power is good, I think that will go a long way to curbing his power. I think his maxband is ok though, it should feel powerful to pull off.
Lich’s Bargain: Great change. You still sometimes Just Lose to board presence, but at least if they cast it more than once you might just burn them to death.
Bone Collector: Ehh I dunno, I don’t think Bone Collector is the reason Necro is too good. If you’re set on nerfing it, I’d just make it 2/3 with Frenzy 1, which retains its identity as a good attacker, while making it weak on defence.
Wight: What does this card do again?
Crypt Crawler: I kinda like this? I do like the flavour of “2 for 3/3 sparkshot” that we’ve got going though. I dunno.
Blue
Porkhand Magistrate: Yeah this is obvious. Makes the ability not terrible anymore. I think this would see actual use.
Lawful Search: I think this change is too clunky. You have to remember this clause after the card has already left play and it’s just inelegant and weird. I think there’s a better way to buff this, or other places to buff Blue starter.
Building Inspector: This is… really good. I like it.
Jurisdiction: The channeling change is good, yeah, love it. The trashing is interesting… it does help you remove deck bloat, but it makes those spells two times max. Although I guess that’s usually enough for most spells, so maybe this is really good.
Tax Collector: Yeah, it always should’ve been like this.
Guardian of the Gates: Seems good. Probably still a bad card, but maybe not.
General’s Hammer: This has the potential to be degenerate, but prooobably not? Might make that wrecker deck even better (Bashing/Peace/Fire(or is it Blood?)).
Drill Sergeant: I think just make him put runes on other units as they arrive (he’s training them) and then give him another ability that interacts with the runes somehow. Like I dunno, “
: Target units gets +X/+X where X is the number of +1/+1 runes on them.” I’m sure that’s way too strong, but something like that could be neat.
Debilitator Alpha: This change has been talked about a lot. I’m in favour.
Spectral Tiger: Yes.
Purple
Time Spiral: Yes.
Tinkerer: Yes.
Prynn: Maybe too strong. Other people have discussed this in this thread already and I don’t have too much to add.
Seer: Yes.
Sentry: This is an interesting change, and I like it. It does mean Present is very strong on defence though, which may be too strong overall. Needs monitoring, but Sentry is so bad it needs some kind of buff, and this is a cool one.
Hyperion: Yeaaah ok. I love Hyperions but this is probably warranted.
Octavian: It’s still bad, but sure. Sometimes you get 16 gold and win the game.
Vir: Yaaay.
KotC: Ehhhh I think this is probably too good. I actually pushed for this in the past, but I’ve come around on it being too fast. Turn 4 4/4 that costs you 0? That’s very strong.
Reaver: Cool I guess? I think I’d rather just give it haste (I know Reavers aren’t known for going fast, but how does it do damage when it warps in?)
White
Fox Primus: Yeah ok, I can dig it.
Aged Sensei: Hmm… I know he’s old, but he is a martial arts expert. And also I don’t know if this is the place to pull power out of White. Hard to say.
Versatile Style: Woah. That’s uhhhh broken. Combine it with Martial Mastery: “Sorry did you want to use that hero? Like, ever? Too bad.”
Hero’s Monument: Sounds good. Maybe one of the best Tech 3s with this change.
Fuzz Cuddles: Yeah.
Masked Raccoon: Hmm interesting take. I think I’m into it.
Bird’s Nest: This might just be too weak now. I don’t know how to balance this card.
Mythmaking: Wooaooah that’s strong. And yet, I don’t hate it… Double Boulder could be obnoxious though. Needs testing.
Ok yeah so that was my unqualified thoughts on that change list. I want to hear other people’s thoughts who disagree with me, because I’m probably wrong.