What kind of help? Im assuming army not painting.

Theodred and Horse - I wouldn't use theodred, give a hors eif you are.
Dwarf Rangers - Yep, go for it but don't rush into the enemy
Black Guard - YES - tough and replace elite troops which may be more expensive or less durable
Uruk Scouts - yes gives you numbers, just flank with them and be prepared to have them die.
Wildmen of Dundling - as above. Not really viable as other things in Isengard do a better job in the same rol.
Faramir and Damrod (Rangers) - yes, I wouldnt bother with osgiliath vets.
Osgiliath Vets - hehe as above. Get rangers instead. You only need a few (3-6 tops) if you are running them as you only get 1 re-roll per fight.
Entire Fellowship - Generally not good but depends on how much terrain you have.
Rohan Royal Guard - a solid choice. use them to take out terror dudes.
Mahur - i like him. 3A = many dead enemies. its only one might point, and you dont HAVE to charge like a cav force would so Im happy to lose the 1 might point.