^ Why do you kill Indonesia? They give you very good Trade Routes since their cities are overseas with large populations, and they're usually friendly with China (unlike psycho Sury) too.
I usually Fort a hill outside the Great Wall - such as the Cotton hill near Turpan - and Fortify a bunch of Pikes and Muskets in it. Barbs will suicide on it and give you some free XP. It also helps reduce Mongol flips. However, the last time I checked the Barb GG point effect of Terracotta Army does not work.