Mesa 17.1 Git is running faster for Civilization VI on all three tested graphics cards, but the performance remains very low...
Hopefully RadeonSI will see more tuning for this newer Linux game in the near future as there clearly is a bottleneck somewhere in its driver stack for this Aspyr ported game. Mesa 17.1 is branching next month.
The Radeon R9 285 and RX 480 were faster going from Mesa 17.0 to the current 17.1-devel code, but the Radeon R9 Fury saw a slight pullback in performance with 17.1, but it's at least still ahead of where it was running in Mesa 13.0.
Deus Ex: Mankind Divided saw faster performance on the R9 285 when going from 17.0 to 17.1, but the Polaris and FIji hardware saw the same performance with 17.1-dev, but at least it's a hell of a lot better than where it was running on Mesa 13.0 stable.