Great report! I'd like to point out that your UOA has lower than average insolubles and fuel dilution. In the 2.0L WRX, fuel and insolubles usually go up to ~0.5% by 5k miles. Maybe GC is the solution for us?
However, I have 20 bottles of Mobil 1 EP 10w-40 to be used so cannot try the GC. I am very interested in how the gold GC does and whether there is any consistency in terms of low fuel dilution and insoluble performance in our Subies.