With batch sparging, a mashout isn't all that crucial in my opinion. I believe the purpose of the mashout is to get the grain temp above conversion temperatures, so that the composition of your wort stays the same throughout your sparge. This is important if you fly sparge since it takes a bit longer, you'd still have conversion going on if you skipped out on this. If you fly sparge for 30 minutes for instance (I'm not sure about times on this, I'm a batch sparger), that extra 30 minutes at conversion temps could change your wort. With a batch sparge, assuming you drain and sparge quickly (less than 10 minutes I'd say), your wort isn't going to change all that much in that time. You're then boiling quick enough, all enzyme activity will be stopped.
I think I made this clear as mud....
Bottom line, I think if you sparged quickly like a batch sparger should, you won't see any appreciable difference whether you mashed out or not.