I think a lot of cards you’re mentioning here are actually fine and maybe you’re just looking at the best case scenario for each when evaluating. Going to put the ones I agree with at the end but here’s some argument for the others
Demon Wrangler - Fine as is since it dies easily by itself and the 5/2 is usually not hard to deal with either depending what you’re playing. And it needs a target so its really weak when played by itself.
Shaytan Assassin - Fine as is since Emperor’s Command now exists and can kill it easily. Again requires a target so its very weak when just played by itself, even though it can gain a lot of value against big creatures.
Scourgeflame Specter - This is essentially R/Y Burn’s win condition and while it is strong, it requires their lands to be close enough to hit the Orb to deal big damage and 7f, so you should see it coming and be able to plan for it.
Axe Grinder - Not actually sure about this one, but it feels fine. Maybe it could get dropped a bit to like 3/3 and more stats put into it’s buff effect, but I don’t think its as big of a threat that it needs to see adjustment.
Underground Brigand - No reason to change this. It sits weakly stated at a 3f 2/3 and even with Gift of Steel, its a 5f 5/6 which is right on par for the stat-cost ratio. Nice effect sure, if you can get value out of Combat, but sometimes it gets removed with Events and you won’t get to use it.
Grim Guard - Another one that is fine. Dies to a lot of the popular mid/late game cards currently and that denies Burn value from the Combat. I’m guessing you’re again looking at this in combination with Gift of Steel.
Groundshaker - As powerful as this can be in certain spots, a fair portion of the time you will get maybe 1 or 2 dmg of actual value from the Gift. And if you have to play this with nothing on board, its basically just a 5/6 for 6f which is on par.
Forbidden Library - This can get a lot of value if you can protect it, but by turn 4 (or T3 with Water Ele) you should be able to have some set up on the board that allows you to react before they are able to start really cashing in. But maybe I just don’t think its that bad since it used to be much worse.
Gabrian Enchantment - This has some really good uses but that’s fine since it opens up a whole archetype. I don’t see the need for any nerf since it is always used in combination with other cards.
Aurora’s Disciple - Disciple needs a lot to get rolling and even then its a pretty inconsistent card, so I don’t see the need to make it even harder to play.
Mythic Beast - Beast is really weak if you aren’t able to play it by the Well. So currently, it looks stronger than it is because Blue is able to get that needed land position so easily.
Baeru - Big late-game creature with an interesting ability. Sometimes it pays off huge and sometimes your opponent can just kite around it. I don’t think any changes are necessary.
Apex Predator - Apex feels fine where it is, it needs another creature although they can use one of yours as well so its a delicate game of not overbuffing a single creature to play around it. Combinations are pretty costly with buffing something first or playing Aurora’s Creation.
Bone Collector - This is another one that is weaker by itself but can really snowball if the sacrifices line up the right way. This is actually kind of a needed card for sacrifice since they give up early game pressure in order to get the big late game Soul Eaters, so if you can get a Bone Collector snowballing it can actually make a huge difference for the deck.
Sagami Warrior & Wood Elemental - I haven’t noticed any problem with either of these currently. Both are really good early collectors but I don’t see either being in the broken category.
Sagami Grovecaller - This card covers one of Green’s biggest weaknesses, having a lack of natural movement ability on their creatures. Without it, Green had always been really weak to other cards which could just kite around them. And the stats are fine for the creature left behind.
Voice of Truth - This covers the other of Green’s biggest weaknesses, having no hard removal in the colour. Without it, Green really struggled to do anything against other big creatures, and specifically GvG matches ended up being just whoever could get the most buffs. Now, there are actually decisions to be made on when to pre-buff or save it.
Soul-Eater - I think this is really close. At 5f, you can’t just play one every turn in the late game unless you have some collection going. I don’t like there’s a huge difference of going to 6f so I could see it getting just a 1f nerf, but I don’t think it needs it.
Windstorm Charger definitely needs something, either a stat/cost nerf or change in the Event synergy to only +1/0. Seifer needs even just 1f to take him back to 6f so its not a loss just using hard removal on him. Hellfire is really frustrating with the rng and the fact of how much Orb damage it can deal. I’ve seen some really cool suggestions about making this target an area on the board, similar to Meteor, and have the damage only in that space. Garudan is pretty close, I think you have counterplay since he costs so much, but I could also see his effect being only 2 damage instead of 3 because his value is pretty insane right now. Crackthorn Beast has ok stats but the rng is obviously the main spot here. Prophet of Tides needs to maybe just move the land once since it gives so much reach with the double movement. Aurora has been talked about for a long time since she is insane value and doesn’t really fit Blue thematically, and there’s been a bunch of cool ideas to change her. Gabrian Archon is pretty close as well since it’s weaker with Blue’s faeria generation engine being weaker. But even just going up to 5f so you can’t play one every turn without collecting could be huge. Wavecrash Colossus I think needs a big change, along with the other Colossus. The minimum cost is a band-aid fix instead of actually making the cards work in a proper way and its too easy for Blue and Yellow to trigger the conditions for discounting them.