Hi BamaStangGuy,
I am in the exact same position as you are right now. I am literally sweating to try lowering our servers load (see
https://vborg.vbsupport.ru/showthread.php?t=148740). During the last 4 days I was dedicated to find bottlenecks and do some fine tunings, and I learned that Memcached is only used to store datastore... Accordigly to memcached stats datastore is only using 0.05 MB... I, like you, initially though it would be used to cache some other stuff as well.
Anyway. I am here to say that I would appreciate some tips on this issue as well. Like you, I know PHP/MySQL but don't know where to start, as I moved to vBulletin only very recently.
Cheers,
Gabriel.