As another post because the previous already got long:
If I may add, one question that I have mulled over is the design goals of having artifacts in the game. Thematically they are great. Apart from that I am not sure what they are there to do. Are they simply another form of advancement (which is fine - it is the very nature of idle games having different, interesting ways to optimize runs) or are they supposed to add another dimension to the game? If so what are they adding?
All my comparison of advancements and artifacts would still be an issue for me, even if advancements and artifacts would achieve completely different things. If all artifact effects would be clearly distinct from advancement effects, you might not directly see the link between the two, but I would say it would be a lack in game design if one was significantly more important than the other.