I need a second opinion, i have graves' disease, it's been a year now since on medication and my ft4 went from 84.2 to 45.2 in a year, is this slow?

Need treatment: The upper range of ft4 in the uk is about 25, right? So your ft4 is still about 2x normal. I presume you still have symptoms. I would advise aggressively treating your graves with Methimazole and beta-blocker to get your ft4 near normal. This can be done over a few months. At that point, there should be a discussion of definitive treatment with radioactive iodine or surgery.