I think Russia is playable as China and USA, in my statistics Russia was often controlled by newbies. Results of these countries depend on diplomacy.
Brazil and USA have non-aggression pact in 50% games and thats why develop well. But eurasian countries constantly fight among themselves.
And EU - is outsider.
Brazil and US only have a non-aggression pact if I control them both.
I never had diplomacy in any of my Imperial games. "Non-aggression" in our games comes from bond distribution and not from table talk. I think Imperial is not made for diplomacy.
BTW, my experience so far:
- Brazil does best, followed closely by India.
- China rarely wins but usually does better then expected (sandwiched between two enemies). It usually catches up near the end because there are a lot of provinces it could grap if it is strong in military.
- US and EU usually do poor. Unlike UK in original Imperial US can´t turtle by controlling the sea and is unable to defend enough provinces.