Cobbler is not good as is. That doesn't mean you'll never use it, but it's slow and heavily reliant on being able to gain cards with +Actions. An extra +Action is more than a slight boost in power, but it needs at least a slight boost. Adding an extra +Action doesn't seem to make it a power card.
Do you have an alternate suggestions for where Lucky Coin should go?
I disagree with your evaluation of Cobbler. If you gave it an extra Action it would be a village Workshop instead of a delayed cantrip Workshop; that would obviously be far too crazy.
Sculptor is also fine. Unlike Cobbler the gaining is not delayed but if you gain non-Treasures the card is terminal. I'd even argue that Cobbler is slightly better as being able to gain the very engine piece you need at the start of your turn increases consistency (Duration draw already increases consistency quite so Duration hand-gain is pretty sweet) whereas Sculptor is more risky, i.e. if you did not play a village before Sculptor the card becomes a plain Workshop (if you want it to use for engine build-up).
Nobody likes Hexes.
I do as the fun of not knowing what will hit you outweighs the downside of extra randomness to me.
Somebody getting a Cultist on T3 that lands on Cargo Ship is to me a worse "swinginess offense" than Alice being hit by Delusion vs Bob being hit by Famine.
That's a two-card cross-expansion interaction. Obviously Dominion has luck, as after all, it's a shuffle game. No denying that. But having a random deck of effects isn't even trying (edit: to hide the randomness. I wouldn't want to imply that Hexes and Boons didn't have a lot of effort going into them. I'm sure they had. But they sure are in-your-face randomness, with no control beyond tracking the used ones.). Personally, I'm also genuinely offended that Locusts just eats Curses without a replacement - as if randomly hitting Locusts wasn't swingy enough. It's like when Jester didn't have the special case for Victory cards. It just spells out "whatever" in bold letters.
What also annoys me, if you were to try to make the best of Boons or Hexes, you would have to look through the discarded cards each time you want to e.g. gain a Cursed Village or play Leprechaun, or play a Sacred Grove and hope it might be nonterminal, to evaluate your chances to hit the right one. That's just painfully annoying and pointless most of the time.
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, you just have to "trash it twice". I think in terms of mechanics and theme, it's much better to not give a 
