Bas Nieuwenhuizen sent out the patch today to enable fast clears by default now that it's working for him on Dota 2 and The Talos Principle. But he's still making it possible to disable fast clears via nofastclears debug option if needed to debug the fast clears support in the future.
The patch has already been reviewed by Valve's Andres Rodriguez as well as RADV co-founder David Airlie who also added a "happy dance" with these latest patches.
The patch doesn't comment on any possible performance gains for Dota 2 / Talos Principle as a result of the fast clears, but once the code is in Git, some fresh RADV benchmarks are probably in store at Phoronix.
Bas Nieuwenhuizen also landed some RADV fixes today into Mesa Git, which are also copied for back-porting to Mesa 17.0 too.