Yea.. I removed the task killer for a few hours and it went from 80% to 40% within the 2 hours or so. So um no YOU NEED A TASK KILLER
Something is wrong with your set-up.
You need to list EVERY application you have on your device.
After a review of them and nothing raises a flag a factory reset is in order.
Task killers are NEVER needed and if you NEED them to get your device to run better or get better battery life there is something wrong.