Leaving botting and scripts aside, because Americans used it a lot, and also this game doesn't have minimap like in WoW etc, so ZR is good for that (no scripts! just minimap no target!), I can say that Russians were always good because they played together. However, it wasn't the chemistry that was good majority of the time, it was the RMT, that they paid to get high levels and gear from adena buying that made them strong.
I have yet to see a party like Polish people used to play in c4 interlude etc, they were a lot better with good ideas of gameplay, and could beat even Russians who came with horde (10x more ppl, zerg ftw). Sorry this server I don't have party but I hope to see your community grow big, so I have what to fight solo 1v2 etc, and even olympiad. You guys play oly?