i got a 1070 back in ~oct-nov 2016. at the time it was for my primary computer. it could mine eth at ~32Mh/s with the proper mucking about with power limits and what not (i think madpacket here figured it out), but the computer was basically unusable while doing that (unlike amd cards, in which mining doesn't affect windows UI or video playback or whatnot - heck i play an old game on my 480 without even turning off the miner). nvidia cards still have this 'issue'. needless to say, since i used the computer ~16 hours a day, mining on it wasn't really an option. so i returned the card to microcenter (payback at then prices was over a year i guess).
oh what could have been.
anyway, point of the story is that 1070s worked fine for mining, problem was you could get a 4GB 470 for ~<$160 any day of the week, while 1070s were >$350. at ~$10/eth, it didn't make much sense to buy 1070s. if those card prices were still available, 1070s still wouldn't make sense.