I made a list of changes for Welder's Workshop a month ago, but since I'm about to go shopping for my semi-annual physical card update, I'm posting here:

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Maul of the Skyclaves
This seems to be a popular switch among cubists. For me, the relative power level of the cards is very close, but the protection effect on Celestial Armor is simply more interesting. It also scores "resonance points" because of the name and flavor. You don't need to ask yourself "what the hell is a Skyclave" when you see this in a pack.

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Grim Haruspex
Grim Haruspex is mainly in the cube because I already owned a copy, and I wanted a lot of payoffs for creatures dying. Her main problem is she's the last card in the cube with the ability to show up face-down, and it's just not that interesting to me. Meanwhile, Abyssal Harvester is absolutely perfect for my purposes since he creates a token copy rather than just reanimating a card.

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Mishra's Onslaught
Electroduplicate is absolutely perfect in this environment. If I had known this card was about to get printed, I might not have picked up a copy of
Molten Duplication. Be that as it may, I'm going to run them both in the cube, because I like effect redundancy in a giant mega-size cube like this. Mishra's Onslaught is getting cut because it costs 4 mana, I guess because it's an instant. I've been running it because it makes artifact tokens, but I don't think that's good enough. It's just boring! It's a boring card!

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Opportunistic Dragon
I've been running this dragon because stealing things is fun, but copying things with a minotaur is fun, too.

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Caldaia Guardian
I really like the Blitz ability on Caldaia Guardian, but I like the spider's payoff more, and I like the flavor more, too. Obviously Welder's Workshop has room for lots of factory workers, but this isn't just an "artifact cube," and I like how mystical Spinner of Souls looks. Plus, there are currently ZERO spiders in this cube! What!?