Re: How much preference should the game give to offense versus defense?
Overall offensive play is more fun than defensive play. The benefits of defensive play should decrease the further along the game gets.
In terms of costs/benefits a team that focuses overmuch on early offensive play should lose out later in the game. The cost of early defensive play (!not camping) is that you might lose a few structures but you will have a solid foundation for the rest of the game. If on the other hand a team stays in turtle mode for too long the costs/benefits should change. They are now losing many structures and no longer gaining much of a foundation for later game stages. The weapons available should reflect that. Letting your opponent anywhere near your base late in the game should be very costly and quickly snowball.