Anyone who says private partying is more skillful is erroneous. The benefit is you get bonus experience while waiting on NM's, but it's not that much more difficult to do. At least if you know what a stun is.

But I went from 12 - 17 3/4ths last night just doing the fate train. So, it's not bad exp in any way.

Can experience per hour be optimized, yeah, and that's normally what the private parties are trying to accomplish. Outside of trying to prep Pazuzu.

But normally I alt tab and watch something to wait for the fate to spawn, in fact I'm basically doing that right now.

The existence of spawnable FATEs lends the instance to be optimized in terms of how people optimized grinding in GW2 -- Get a zerg rolling.