Cards you listed tend to be good in Pandora, but majority of them is way worse in constructed (normal ranked).
*Magda - really easy to remove, even if you play it in spot you think is safe (cards like Flameburst, Wind Soldier, Ninja Frog).
*Shara - same as Magda, dealing 3 damage isn’t that hard + buffing her makes her really vurnerable to cards like Frogify or Last Nightmare.
*Day of Dragons - The cards seems good, but since Orosei (one of the dragons you get) is one of the worst pieces of RNG crap in game you don’t really wanna play it.
*Hammer of Acros - the only way to get it outside of Pandora is is to trigger Baldurions corrupt ability, which isn’t easy if you aren’t already ahead/your opponent made aggresive lands he can’t protect for no reason.
*Mobie,t Azure Skywhale - Mobie needs 8 special lands to be played, dragons only 2, that’s why he is stronger. changing his stats to 4/4 would make him killable by cards like Firebomb or Punishment - that’s a really bad idea. Also moby isn’t really that good unless you are either far ahead or you opponent has only overbuffed giant creature
*This card is alreadypretty bad, even in pandora. Nerfing it more would be just cruel.
*Emperor Kaios - as Magda, only good if you are far ahead or your opponent has no aggresive lands or global removal (like Choking Sand). That’s rarelly a case in ranked enviorment.
*Frog Tosser - card is strong, but not strong enough to be nerfed. making it 2/4 would make it unplayable.
*Gift of the Rakoa - as much as it can be unpredictable you often will find yoursefl unable to play it as enemy simply removes all your creatures.
*Istanu, Eternal light - as in case of Mobie, you need 4 more lands to play it, that’s why it is stronger. This card would be op, but the sole existance of Garudan and Frogify make it balanced in constructed play.
*The Tree of Everlife - you need 10 special lands to play it, which makes it really s l o w. It also doesn’t trigger instantly, so you have one turn to react.
*Yakkapult - you usually increse it stats to protest it from being destroyed, not to increse damage. Giving it divine (god mode) would actually make it cheating card.
*Runnin - i agree with you, this card is really annoying, though simply increasing the cost would just make it unplayable, and I don’t think that’s the correct way to solve the problem. Also, as much as we may dislike being forced to endure Runnin, many people do enjoy playing decks including her.
I understand you get annoyed by those cards in pandora, as it is harder to play around them in there than in the constructed, but you should remember that the game is mainly balanced around constructed play, not pandora. As for the new mode idea, I belive there actually was mode like this (only one copy of the card in deck), just before they opened pandora. From my memories matches in this mode felt way more random and less satysfying to play, though it was few years ago so I don’t remember it to well.