Are those 8GB models or 4GB ? RAM overclock seems high for 4GB models - I can get at best around 1950 or so with 4GB (Elpida)
For the RX470 Sapphire's I get about 2025 overclock.

I will work with you on that if you wish - but give me some time to do tests...

-mclock 2025
-cclock 1150
-cvddc 950
-mvddc 950

That's my setting for the Sapphire RX470 OC 4GB