Still, 12/12 is not 25/28, one minion is easier to remove than three (you can have cheap single target removal or silence for 1-3 mana, but not AoE) and buffed Edwin won't give you +4/+4 for all your minions until the end of the game. It's way too much value, way too early.
Besides, does the fact that Edwin has been in the game from the beginning make him more fair? After all, a lot of classic cards ended up in the HoF, because Blizzard felt they were bad for the game. Heck, Innervate was nerfed once, because Blizzard stated that mana cheating (which leads to too much value too early) is wrong! The game shouldn't be decided that early just because your opponent had lucky combination of cards. On a larger scale it's not OP, but it's definitely stupid and frustrating for the other player.
1. The card itself would be balanced if it gives no rush. This way it is retarded. Summon 2x5 mana premium beasts and clear two minions like seriously OP as hell for 7 mana(which is played on turn 3-4 regularly). Or summon 4 mana or less beasts only.
2. Lightning bloom should only make next minion 2 mana cheaper instead of giving mana. So no spells and no stacking. 3 Overgrowth should be 5 mana. 4. And Kaelthas should make your third spells 5 mana cheaper so no 10 mana BS.
4 is a must any 2 of 1-3 should be enough for a nerf.
Druid by no means is op. Is just mindless, boring and uninteractive. All druid decks have been reduced to a good mulligan. If ramp + guardian animals in hand = most of the times gg. Yes, some classes can counter it. That doesn't denies the fact that all games with druid are THE SAME. Even Maly druid wins most of the times by this... Imagine a Malygos deck that doesn't needs Malygos to win most of the times lol.
It's not that it's OP, It's that it's a do or die deck. It's a very bad gameplay experience... Sometimes for the player sometimes for the opponent. You either draw the good cards and likely win, or don't and likely lose. Of course that's simplified a little, but the deck probably swings from like 30% win rate to 80% depending on if you draw the ramp etc. So to the loser it "seems" OP because it curb stomps you so hard if it draws correctly. Really it's a kind of deck that probably shouldn't be in the game, but it appeals to timmys