Black orcs are good just for the varity. equip them with shields for a 4+ as against shooting etc then in combat you can either go hw and shield for 4+ as and 6+ ward with single strength 5 attacks or if you come across a horde of weaklings swap the shield for additional hand weapons or against monsters or cavalry etc go great weapons. they are prepared for most combats. and the choppa rule means +1 strength in the first round of any combat meaning you dont need the charge, the +1 for charging aint much compared to how much they (should) kill during the actual combat.
all this and then of course any black orc characters that a no doubtedly in the fight aswell and any magic banners(mine go for the flaming attacks)