If you're shooting split finger with an already large gap, then the broadhead will add some length. But if you're shooting 3 under with something in the 25" or less gap range, length of point shouldn't matter much at all since Most of the broadhead is hiding behind the shaft. To me, a broadhead looks the same as a field point but with thin little wings coming out the sides.
Before playing with your nocking point, try changing your broadhead orientation. Mine do all sorts of funky turns when they're oriented any way other than perfectly horizontal (perpendicular to the string). I've had them heading straight and dip in the last 5-10 yards. I have a working theory that as the shaft bends in paradox, the broadhead also wags, causing some wind deflection. If the heads are oriented to "slice" through the wind, the effect is less than if the head acts like a paddle. That's just a hypothesis, however. All I really know is that as long as my heads are aligned horizontal, they fly consistent and straight. Any other way and my groups more than double in size and I see all sorts of wacky flight. I know some folks here say that orientation doesn't matter at all to them. But I won't do it any other way now -- the results are too predictable when I'm the one pulling the string.