You definitely want Vrasku, and an Uruk-hai Shaman.
Maybe even another Captain, so that you can have one with Shield and one with Two-Hand (devastating with Strength 5).
Mauhur is a good choice, but Vrasku should have priority over him.
If you are allying in Goblin Warriors, you should consider fielding Ugluk, as he can sacrifice the lousy Goblins in order to gain an automatic 12'' Stand Fast! Some tactics involve just having him hang back or always making sure he is supported by a couple of Goblins, so that they are ready for the cleaver when the time is right..
Do you have Grima on horse as well? I think he is even more useful on horse.
Also perhaps aim for more elites like the Berserker or Feral Uruk-hai (cheaper version)?
How many of your Uruk-hai Warriors have Crossbows?
Also the most important question: how would you like to develop your army? What is your preferred playstyle and tactic?