This is always an interesting topic because honestly there are a ton of variables, and the solution can be very rider specific and location/terrain specific. Plus I think many mountain bikers try to apply everything they learned from their pedal-only bike days to their emtb's. Is there carry over in bike geometry and setup from one to the other?...of course there is. But these emtb's with their added weight, battery location, and power assist can alter traditional thinking and setup in some ways.
The weight contributes to stability and lack of easy deflection with little to no penalty because of the pedal assist. The center of gravity on these emtb's often have a front end bias benefit due to battery location which removes some of that effort to put more rider weight forward and over the handlebar. And then the power benefits often require a little different rider approach to entering, leaving, and through the corners at more speed. Some dirt motorcycle techniques can come into play if you're riding one of these aggressively.
OP, you mention front wheel washout. Obviously tires also come into play, so I don't know what you're running there. I'm on a Rail 7 and run 2.6 Minion DH tires front and rear. Pedal assist allows almost no penalty for the bigger tires and actually a benefit since you can hammer corners with better traction. I also run a very high bar with the OEM 50mm stem and a Hussafelt DH handlebar. In profile the bike looks more DH than trail, but the bike still rails the corners without me having to be permanently hanging over the front end of the bike like a Tour De France racer...LOL!
I'll say it again...though you don't throw out the baby with the bath water when it comes to bike setup from pedal-only bikes to these emtb's...you can usually apply a wider latitude of geometry and ergonomic tweaks to emtb's in many/most cases that are not dictated by traditional mountain bike standards.
