Orcs are quite good fighters, and they have no weak points.
Dwarves have the cult, hidden threats (bloodbeasts, necromancers, werebeasts, spies), diseases, the red-marker easter egg, fire-starting reactions... Orcs do not have anything like this.
Increase frequency of invaders: The thing is that the good races only have one active season. They can only siege max once a year, or send an ambush once a year. Goblins and Orcs (which trade soooo often with you when you play orcs) have multiple active seasons, and therefore attack more often.
Frequency could be raised by linking syndrometrigger to force-siege, and make every orc start a siege ~1% once per year. This way you get 1 extra siege a year if you have 100 orcs, and ~2 extra sieges a year if you have 200 orcs.
It would naturally decrease and increase with the amount of orcs running around your camp.
Edit: Found a little typo: In your SCALP_TROGLODYTE it says "troglodyte:orcs:orc".
[CREATURE:SCALP_TROGLODYTE]
[NAME:troglodyte:orcs:orc]
[USE_MATERIAL_TEMPLATE:MUSCLE:SCALP_TEMPLATE]
[SELECT_MATERIAL:ALL][ARENA_RESTRICTED][DOES_NOT_EXIST]
[REACTION_CLASS:TROGLODYTE]
EDIT: Would it be ok it if I add a " skin" to the names? I know that a scalp already implies that the material is skin, (human scalp is obviously the skin from the head of a human), but as soon as you use the materials for other objects its not clear. "A human-bound book" or a "human journal" sound very... normal. As if a human made these things, or if they belong to a human.
"A human skin-bound book" or a "human skin journal" sound a lot nicer.
I also added scalps to the FD races. One generic "skin scalp" type. Is that any problem for orcs? It was requested in the Warlock thread, to be able to use those sapient invaders for it as well.
[EXTRA_BUTCHER_OBJECT:BY_TYPE:THOUGHT][EBO_ITEM:MEAT:NONE:CREATURE_MAT:SCALP_FD:MUSCLE]
[CREATURE:SCALP_FD]
[NAME:skin:skin:skin]
[USE_MATERIAL_TEMPLATE:MUSCLE:SCALP_TEMPLATE]
[SELECT_MATERIAL:ALL][ARENA_RESTRICTED][DOES_NOT_EXIST]
[REACTION_CLASS:FD]