Rob is right. There are a multitude of things that can makes arrows shoot crappy with broadheads. Misaligned heads/inserts is one of them, meaning not concentric with the shaft. Incorrect arrow spine is another. FOC that is too low. Poor bow tuning or lack of tuning. These are probably the most common. Heads with a lot of blade surface don't make things easy either.

While I'm talking about alignment with the shaft let me clue you on something else. Once you align a head to a particular shaft you should never take it off. If you remove it and reinstall it again later there is no guarantee that the head will seat to that insert the same as before. It has to be spin tested each time.

If you have carbon arrows you cannot heat the inserts. They are put in with some sort of "super-glue" or epoxy. Heat will only destroy the resins in the shaft rendering that shaft destroyed. If you are bent on aligning the fletching with the heads thre is only one way to do so. You have to strip the arrow and refletch it, indexing the nocks as you need to.