Are you sure? That would make it more profitable than mining Ethereum. Every Zcash forum i have read about the rx470/480 suggests that they average 30sols/s
Yes. The threads you've been reading is probably a couple of months old. Zcash is a new coin and a lot has happened since then. Just check the Claymore thread for ZEC, it clearly states more than 30 Sols/s for all its examples.
As a quick example, my two R9 Fury Nitro's gets 460 Sols/s each when undervolted. So yes, I'm sure that you won't be getting 30 Sols/s with an RX 470. My 470 and 480 gets around 300 Sols/s. Stop looking at old threads on the Zcash forum.