When I am honest with my pdoc, she usually can see where I am coming from and will approve the change that I am requesting, such as lowering my meds when I give her a valid reason. I think having a pdoc that takes your concerns seriously is very important. Your reasons for wanting to lower your medication.
If your pdoc can't understand your needs, then I would question whether to switch to someone else. I hope you have a pdoc who you can trust and be on the same page with. Either way, definitely bring up the fact you switched meds to avoid any potential concerns, such as problems tapering that sometimes catches up with you later on.
I can actually totally relate to your med concerns and have reduced for Seroquel on my own, although I do not recommend it. I have never been on prozasin though. Once I told my pdoc, she allowed me to stay on the lower dose at 400 mg. At 600 mg Seroquel, I would feel my blood pressure drop and almost pass out. Once it was reduced, I was feeling better. I did not have problems tapering down, but that's just my experience. Now, I am down to 300 mg and plan to only increase it to 400 mg if necessary. I no longer ever want to be on 600 mg. It is scary.