mine varies as well, usually in the 20-40% range, sometimes it is very low, other times it randomly shoots up in the 60's, which drains the battery quick. doesn't seem to happen as much since the OTA update tho.
Also depends on how low your battery is at. Mine Android OS is at 35% right now, but my battery is still in the 90% range. So that is 35% of only that small 10% of the battery that has been used so far. When I click on Android OS CPU time is only 9m out of the over three hours it has been unplugged. So in that case then no that is not a problem.
My battery is at 60% and my OS has used 54% of the battery. I have been off the charger 10:34. I did some light web surfing, played Quisr for a few minutes, left data on constantly and received read and deleted about 20 emails and texts as well as a few short voice calls.