worying about battery life is another matter you can either not get this app or anything that drains your power and just use the phone as a phone or you can benefit from as it is created to be a smart phone and not worry about battery life.
As for being able to be offline you can always activate flight mode or turn off wifi or data package.
Not being rude at all but this is how its supposed to be.
I also have a nokia E7 and have installed a task manager can kill any unliked app i don't want running, you can always have this option also.(not that i know about any task manager for my n9)