If the phone is doing nothing, the OS will consume close to 100% of the power (because nothing else is consuming power). The only time there's nothing at all consuming power is when you remove the battery.
It's not the percentage of power that's being consumed, it's how much power is being consumed. If the OS consumes 98% of the power, and a charge lasts a week, you have a great phone. If the OS consumes 2% of the power and a charge lasts 2 hours, that's one of those phones that the robber won't steal from you even if you beg him to.
You're worrying about the wrong thing. Can you use the phone almost a whole day without charging it? If you can, it's about normal.