Well this seems like a relatively solid list, but I think there are one or two things you may have overlookef that would make it much better if they were applied. First off i'm sure you are aware that Durburz and your shaman should always be together, as you get an instant 12" standfast, but incase this wasn't a loophole you were aware of, then there you go
Onto my other points, you called your last warband your 'spec ops' force, and while i understand why you would use that terminology, as everything in it is an 'elite' model, but moria 'elites' are sub par compared to most other armies, a blackshield is only fight value 2, and a prowler with shield is only defence 5, a dwarf warrior with nothing is better than both of them. Moria elites only really come out of their shell when in great number, if you convert all of your shield goblins to prowlers, you have a whole frontline equipped with throwing weapons, and the models are actually undercosted by a point, so you get mroe bang for your buck.
Also I think I would go for a Gundabad Shaman instead of the captain. With only 3 fight value he will need to call a heroic strike to even win a fight against any good hero (bar some stupid ass hobbit), whereas the shaman has a good chance to permanently disarm an enemy hero, especially at 500pts where the most common good heroes are people like Rumil and Erkenbrand, who only have one point of will to resist spells with.
I hope this helps.
P.S: Warg Marauders are easy to convert and probably the most powerful for their points unit in the game.