Love it!
The shadow looks absolutely sweet. I missing the synergy with the Brute, this particular morc build doesn't seem to care about burdens. Perhaps cut them for to finish out your set of Ambushers and Spearmen.
Can't go wrong with an odd copy
Gothmog, Morgul Leader or two. Sure he's not on culture, but 3 arrows with a 15 strength beat? That's pretty sweet.
I'd maybe keep a single brute and up to 4 each the Spearmen and Ambushers. Perhaps cut the last lonely brute for
Stronghold of Minas Morgul?