Good point, sandbagging does take away the fun of the whole alliance working together. Which is what world wars provide, a way to strategize and win together as a team. Without that, dominations is a solo game pretty much.
One other point on balance... it is a LOT harder to max defense at a given age than to max offense. Which is think is why offense is usually easier and has the edge (and it should be that way). Many people have maxed Atomic age armies, but not many people have maxed Atomic age defense. So surveying at 30,000 feet all the battles taking place, it would be easy to mistakenly say that offense is overpowered. Maxed offense and maxed defense of same age should be balanced, not maxed offense of age n and maxed defense of the age n-1. I really hope BHG fully realizes that point.