The difference between 8 and 16 GB RAM sounds nuts to me.
I've been using a 1070 for the last 10 days and framerates are fine in ED when I use the Vive, admittedly I'm not monitoring them constantly when using the HMD but I'd notice if frames were dropping.
I'm currently using an i5 6600k, GTX1070 (MSI Gaming X) and 8GB system RAM (maybe the difference is that mine is 3000Mhz DDR4?). The last session I played was with VR High, SS x1.0 in game, and SteamVR targetMultiplier at 1.75. The buttery frame rates I got would run contrary to the game needing 16GB RAM.
Just as a comparison, last night I decided to play on the 1440p screen instead of VR and had hardware monitoring open throughout the session - running 1440p, with in-game SS x2, quality set to Ultra. I was getting frame rates between 60 and 70fps, and system RAM usage maxed at 5.9GB, a little less than the 6.2GB video RAM used by the GPU. It looked fantastic.