Isengard army list help needed

So I've never really played LotR bar one intro game at my local store but I'm feeling Isengard as an army simply because the Uruk-Hai are just so damn cool. However I could do with a bit of assistance...

I'm not sure if the usual size of a LotR game but I have a vague idea it's 600 points? Here's my first ever bash at a list, please feel free to tell me where I've messed up or I'm just being plain daft:

Warband: Uruk-Hai captain w/heavy armour, shield
7x Uruk-Hai w/shield
4x Uruk-Hai w/crossbow
1x Uruk-Hai w/banner

Warband: Uruk-Hai Shaman w/Armour
8x Uruk-Hai w/pikes
4x Uruk-Hai w/crossbows

Warband: Sharku w/Warg, shield
3x Warg Rider w/shield, throwing spears
1x Isengard Troll w/spear

So that comes out at 599 points and 31 models, giving me a breakpoint of sixteen. I figure I have a decent combat centre of Uruk-Hai with shields backed up by pikes/crossbows and a shaman then a troll for anything nasty (I'm looking at you Aragorn...). Plus I have Sharku and his boys for flanking/hero hunting etc.

So I figure maybe I'm a bit thin on the ground? 31 models doesn't seem an awful lot to me and a sixteen model breakpoint is quite disconcerting. I also suspect I should probably drop a few of the pikes for more shields to beef up the first wave, or maybe more crossbows?

The only models I've actually bought so far is the Uruk-Hai boxed set with five pikes and five shields so I'm open to any suggestions you have.

Any advice would be grand.

600pts is a decent sized game yeah.
On reflection I'd thinkk over the following;
4 Warg riders ain't many.
A musician may be a good investment.
That's all at the moment.

Needs Shagrat. Or whatever he is called. His ability to knock down enemies is incredibly OP. Bring a Task Master to give him 4+ free Heroic combats/ Heroic strikes and you're laughing.