Donald X is on record as saying he wouldn't do Hexes in hindsight, so thinking about the official Doom cards (I posted something like this a few years ago in a different thread).
Werewolf
Action/Night - $5
If it's your Night phase, gain a Silver. Otherwise, +3 cards
Not a bad consolation prize for drawing it dead, and sometimes you'd intentionally play it at night.
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Vampire
Night - $5
Gain a card costing up to $5 that isn't a Vampire, then exchange this for a Bat
Bat
Night - $2*
Trash up to 2 cards from your hand. If you trashed any, exchange this for a Night card.
Vampire doesn't need a buff to make up for losing the hexing, but just to be fair I changed Bat slightly so it can transform into an Exorcist or a Raider or a Den of Sin (might need an awkward "exchanging isn't gaining" clarification in the FAQ however for the "gain to hand" night cards)
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Skulk
Action - $4
+1 Buy
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When you gain or trash this, gain a Gold
Skulk is on my veto list on Dominion Online so I'm not sure how strong it is, but my impression was the card would be fine without the Hexing. When trash bonuses are fun though.
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Leprechaun
Action - $3
Gain a Gold. If you have exactly 7 cards in play, gain a Wish. Otherwise gain a Copper onto your deck.
Envious (as a "while this is in play" effect) is probably a better fit, but this is nice and simple.
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Cursed Village
Action - $5
+2 Actions
Draw until you have 6 cards in your hand
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When you gain this, put a card from your hand onto your deck.
Just like with official Cursed Village, it might hurt, it might not. This version can also be helpful.
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Tormentor
Action/Attack - $5
+$2
If you have an Imp in play, each other player gains a Curse. Otherwise, gain an Imp.
Incorporates another good idea from the forums regarding Imps (not sure who had it first - maybe it was LastFootnote?). May not need the Cursing but I like the idea that the little Imps are helping the Tormentor do mean things.