Mines drop around two percent after removing it off charge. Two % I've heard is considered normal. Even though you're rooted - I don't think it should be doing that. Rule of thumb; check to see if battery is holding its charge. You can check the battery life. Note: Not because a battery is new...that's an implication that it is GOOD.
Ive been having a similar problem with my extended battery. The first 10%-20% goes by quickly. It depends how i charge the thing. I was reading the worst thing to do with a li-ion battery is letting it die out completely frequently changes the chemical balance with the li-ions. Letting the battery drain almost completely helps the battery gauge accuracy, this only occurs when u give it partial discharges & charging creates digital memory unlike niCAD batteries that have a charge memory that got to be drained completely to calibrate them. When i give partial discharges my phone life improves unlike when i drain it completely. Ive also used setCPU to set up a profile & it saves some juice.