Bah, it's four in the A.M. Here's some data.
Top 8 Results
Of note, the Paradoxical lists with the asterisks contained Monastery Mentor as their primary win conditions. Neither list was the standard 4X Mentor Outcomes, but rather eccentric lists from players such as @iamfishman and @brianpk80. These lists contained 2 Mentors each, with Brian running one in the SB "to come in against other Mentor decks". If counted as part of the Mentor archetype, that brings the total up to 28.4%.
This breakdown is based on archetypes and not tags. The actual percentage of Mentor in the metagame is slightly higher. Unfortunately, data collection has been inconsistent as Ryan and I have missed events and relied on others to help us. It's a significant amount of work and we are immensely grateful to @desolutionist and others for that help. However, we don't have tag breakdowns available for every event. The percentage of Paradoxical Mentor is typically low, normally 2-4 players on a given day. A reasonable approximation would put the percentage of Mentor at about 25% of the metagame, or on par with Shops. Again, these decks aren't necessarily focused on Mentor and the number of copies is pretty variable, but since Mentor is currently on the community's radar for restriction, it's best to keep the metagame saturation in mind.
Archetype vs Archetype MWP
The color codes are as follows. For win rates, green corresponds to >50%, red to <50%, and yellow to =50%. The problem with establishing a range is that the sample sizes (and therefore uncertainties) aren't consistent. We expect much more variance from the 3 matches Eldrazi had against Blue Control than the 171 matches Mentor had against Shops. The second table shows those match breakdowns, with green corresponding to >50, yellow 25 to 50, and red <25 matches. I'll leave it to the readers to discuss the implications of this.
Trends in Major Archetypes
Just to show how variable win rates and even metagame percentages can be on a weekly basis. Also, it looks that Shops is trending upwards in metagame percentage while Paradoxical is trending down.
It's 4:00 am. I'm going to bed.