I think your question is a very valid question and one that I still wonder from time to time.
My tumor was believed to be about your size in scans, but was actually 10 mm. I think that depending on the size of your tumor and location it can influence how many hormones are affected.
I am 4 years post op next month and have had the best few years of my life. Recovery was very long for me, but I had more than my share of complications (about 1 1/2 years), but almost everything is better now.
I am panhypopit and probably always will be, but once it is adjusted it is a little annoyance more than anything. Due to lack of hormones I am only down 35 pounds from my high. ( I should be down another 50-60). That is really my only complaint.
My memory problems are worse post-op. I can't for the life of me remember numbers! Everything else is about the same.