my iPhone 4 battery seems to have worse life with IOS 6, not sure with iPad. As for neccasary Nope, it is actually a waste of time i would say, it is missing useful stuff, and added worthless stuff. It is weird that it is not offering IOS 6, how about try to update plugging into iTunes on a computer maybe? not sure, try updating to the 5.1.1, then see if after that it offers 6. but it is not needed

hope this could help