Since I've hit v16 i haven't seen a single shoulder drop from keys, and I have used 40+ keys (20 of each silver/gold) and haven't seen any shoulder peices at all.
I have plenty of v15 and lower pieces from when I was using the random key @ lower levels, but none @ v16.
Can devs confirm if the drop rates are the same and I'm just being punished by the RNG gods?