One drop design is this interesting thing. It's really awkward to design them right. The thing is that in the agnostic game "mana efficiency game" the abstract concept of, what if i built a deck with 1s, 2s, 3s, etc, how would I maximize my chance of spending all my mana every turn with minimal use of hero power to do that, in that minigame, one drops blow. They blow at that in Magic too, and they blow even harder in Hearthstone. So if you want to entice people to actually play one drops, you either need to give them the busted warlock hero power, where the mana efficiency game is trivially easy using any deck and just activating hero power the appropriate amount of times, or you need to hand out one drops that give so much meaning to being 1 pt. ahead on your mana efficiency early on that they are insane. Which means you basically need to make them as powerful as two drops, but then print 1 on their mana cost and pretend its ok. It's a lot easier to get away with that if it's Mana Wyrm and class restricted. Anything neutral is gonna become pervasive.
You really don't need turn 1 one mana creatures to make a good card game, even though Blizzard seems to think so. Playable one drops are inherently swingy since they provide you some tempo in the first three turns, but do nothing if you draw them later on. If they're not in your opening hand, they don't offer anything to the mana efficiency minigame. 1 drops like Earth shock and abusive sarge are different, of course, those are good.
I've watched zoo mirrors in modern in mtg, which revolves around 2 mana quality 1 drops duking it out. I haven't ever found it particularly fascinating.
I think it'd be a good plan to keep all neutral 1 drop turn one plays at about leper gnome power level where only warlock is interested in them, and let the other eight classes design strategies around turns 2-10 instead of printing stuff like undertaker that forces people to play that one drop just because it's a 2 drop.