Thanks for the kind words!
To answer your questions directly:
Testing even three decks against each other, interpreting the data, and doing a complete write up is a very time consuming process, and I felt that adding a forth would simply have made the article too long, redundant, and would have taken too long. I selected the three Shop variants I did simply because I felt that they were solid performers and among the more popular types of builds that people would be likely to play. I didn't leave 5c Stax out because I don't think its a good deck, or because I thought it wasn't competitive--rather, because from my vantage point I haven't really seen a lot of people playing the deck. Now, it is possible that it is more popular than I am perceiving, and I would certainly welcome people who have experience with 5c Stax to post in this thread and contribute that data to the conversation.
I would hypothesize that the decline in popularity probably has more to do with the fact that its need for more colored mana sources makes it more difficult to take advantage of Lodestone Golem the way that Mud decks can. It seems to me that Lodestone Golem is one of the strongest incentives to play Workshop decks in the first place, as it really leverages the advantages inherent to Workshop strategies over non-shop decks.
Secondly, I didn't do any sort of exhaustive testing of the
www.dec against the Vintage Gauntlet. The point of building that deck was ultimately a thought exercise that sought to use the data and theory I had learned about Shop mirrors to build a Shop variant that my testing suggested SHOULD exist, but didn't. I am sure that because I didn't actually test the deck against an imaginary field, that there are a number of small tweaks that would probably improve the list--for instance, my teammates suggested playing Triskellion over Lightning Bolt in the sideboard--and I would guess that is probably correct.
There is an RIW 10 proxy tournament at RIW hobbies on Saturday December 4th, and I am strongly considering playing a tuned version of
www.dec list at that event. I would very much enjoy writing a follow up Workshop article titled: "How I Won a Time Walk with
www.dec!"
I hope that my response answered most of your questions; if not feel free to repost or hit me up via pm.
Also, if anybody wants to chime in with results (testing or theory) about how 5c stax fits into the Workshop equation, please do.
Cheers