But that's 385 / month revenue? On a setup that's what, $3400 to buy, for seven 1070s? Seems like asking for 10 months to cover capex is a bit thin, given the price instability.
Miners shouldn't be meaningfully exposed since they can sell off their ETH as soon as they mine it (deposit it to an exchange address and sell off every few minutes via an API, or something like that). And while ETH might crash enough to make it no longer profitable and risking your capex, you can switch your GPU to mine whatever is most profitable, so you're more diversified than it looks and insulated from the instability.
Resale value on the GPUs is also worth monitoring. While it remains high enough, you can discount much of the capital cost because you'll get a high fraction back if you decide to sell the cards.
Miners don't want to push their GPU's that hard, a hardcore gamer may overvolt their card to get a more stable overclock but a miner will undervolt it to run it cooler and increase the life of the card.
I'd rather buy a used Fury X off a miner than a gamer.
Buying ASICs is high risk and (probably) high reward - in event of crash you are left with worthless machines. GPUs will still have some value, even after all crypto currencies drop.