The main message is that game designers should be able to code. Code is the tool of the trade. (http://bbrathwaite.wordpress.com/2011/03/01/built-on-a-foundation-of-code-game-edu-rant/)
I agree that one should be able to design dynamics for games. Designing dynamic is to design code. Understanding algorithms, state machines, behavior trees can be extremely helpful for game design. This said, knowing rudimentary coding can be helpful, knowing more software design can be more helpful. How much one should know about software design to be able to design games?
But would math and excel skills also be used for this?