So every now and then, SSG releases new MM entrees, most of the time for newer-pack stuff. But we still have yet to see fire, storm, earth, and sky giants. Hill giants made it in no problem, but where are their elemental counterparts?
Fire beetles are also missing, as are crabs, and kelpies. Dryads too, I believe.
I am probably missing some things but you get the idea. Lots of commonly-encountered mobs are absent from the manual.