Here is a list of suggestions that would help with these problems:
1) Make it possible to reduce travel with turq. When you have already sent your troops you should be able to spend turq to reduce travel time. This will make it easier to coordinate several walks, and help avoid attacks timed with nahuals.
2) Only build cities some distance away from other tribes. This would prevent the strategy where some tribes place low lvl cities close to other tribe's hives and hit them with troops from their own high lvl players.
3) Make all killed troops go automatically to Itzna Temple. This would keep many players playing after they got killed.
4) Write a better guide about how to avoid attacks. Many players simply don't know how to stay alive in this game, even when they have been playing for years. Some ppl just start on new servers every time they are killed. You could perhaps even make a tutorial about defense.
5) Make it possible to research better survival rates when you are killed.
6) Remove flags from ppl's profiles on the international servers. It is way too easy to guess when ppl are sleeping when you can see what country they are in.
7) Make it possible to slow down enemy attacks using either research, buildings or some new unit. This would give you better time to coordinate your defense or escape. Speed kills