As Art Director, I feel I can shed a little light into this that might help make sense of some of this. People see the finished product and then proceed to make assumptions about how it got there, which aren't always accurate. We have a great squad of artists right now with a varied set of strengths who love working on Doomtown. Everyone has their favorites, which is great, and we're really happy about that. However, criticisms can pop up from time to time that get directed at artists, but to be fair, they're really more a result of the process and the challenges that the Doomtown Team are faced with from time to time.
RE: reliance on studios - We only have one studio that we have used since I've been handling the art direction, and I believe that's consistent all the way back to the Base Set, at least for the most part. We use them because they can handle a larger load than most of our other artists, which comes in handy when we have a large order. They also consistently churn out quality work; if they didn't, I'd be looking elsewhere. They have produced some really great pieces for us that you have seen, and a number to come that you haven't seen yet.
They are also essential for when an independent artist decides that he/she cannot finish their illustrations as assigned, leaving us in the unfortunate position of having to re-assign pieces for a fast turnaround in a short amount of time. It's not fun, but some of the artists we use regularly (studio or otherwise) are great for the "clutch" moments when a deadline hits and an artist has to back out on on a commitment for whatever reason. For example, during the Dirty Deeds - Bad Medicine batch, I had an artist back out on three illustrations at the last minute that our studio was able to pick up and turn around very quickly. We have other independent artists that are great resources for that too and they've really helped the game out in big ways in the past.
RE: diversification of eggs - If you read Dan Knight's article on the playtest process, you'll remember that all of the Saddlebags are created in groups of three. So for example, Dirty Deeds, Foul Play, and Bad Medicine were all created together, which means the art for all three was ordered and assigned at the same time. It's not until the very end of that process where the allotment for which cards will be placed into which Saddlebag occurs. So while I have no intention of putting a whole bunch of pieces from one artist into the same Saddlebag, sometimes that's just how things get divided up in the end and there's not much I can do about that. Those decisions are largely driven by a need for diversification of card types and mechanics as well as the depiction of key story moments, etc.