Aside from the droid, nothing is really that much harder. Bosses will hit for a bit more and have more health but that is it. We have cleared EV on nightmare up to Soa, and cleared hardmode EV (With Soa, pre-patch) last night.
Is nightmare mode EV excluding Hardmode SoA easier then Hardmode SoA
Gear is very buggy in nightmare mode though. We have had only mods and schematics drop from two bosses last night, and one of the bosses dropped columni instead of rakata gear. My advice would be to stick with hardmodes, as you get a chance of getting rakata as it is not a constant on nightmare.