It doesn't help that the main character is as Monotonous as Heero, or that the heroes have superiority over their foes. Really, is there a reason they should sound stressed or excited?
At least the Flag guys sounded enthusiastic. Their voices were probably the most notable.
It's actually nice to see normal politicians in a Gundam series. In most series, Gundam doesn't show the main politicians, and when we do, they always eccentric and have a crazy plan. Here, we have simply normal politicians doing normal political things.