All helps... My 2nd home (primary res), I had to sell fast. It was July 2014 in Phoenix and the market dipped right when I listed. Appraised at $440K and I sold for $335, after listing at $420, then dropping price drastically every week till it sold. I bought it in 2003 for $255 and only owed about $140, so I still walked away ahead... If I could have stuck it out and waited a month or two, I could have got $400K. The zestimate is now $422K, by the way.
So, if at the time, $400K was the FMV, and I sold for $335K, that's about 85%.... So, yeah, you're right, 0.7 is too aggressive. At 0.85, someone will snatch it up fast.
I like looking at the sales history of houses. If the seller has a ton of equity, they might be willing to sell for 0.85, easier than someone that must sell for full price just to break even. You never know who is motivated to sell, tho. I think I'll start making some 0.85 offers and see if I get a bite.