You've got lots of fun stuff to play with there and a Helm's Deep style Uruk Phalanx is a very cool looking army. However, you're missing the two best Isengard unit types in the game: Feral Uruk Hai and Crossbowmen, they are absolute game winners.
Don't get me wrong, the models you have will be more than competitive and Isengard can make a whole range of really solid armies but if you're looking to make a really effective and terrifying force then Ferals and crossbowmen are absolute game winners.
As others have said you're also lacking a few key named characters, Vrasku, Grima and Mauhur (in that order IMO) are all great choices for an Isengard list:
I can't remember exact points but something like this is an incredibly effective 750 list:
Saruman on horse and Grima
2 Beserkers
5 Ferals
Lurtz
7 ferals
Armoured Shaman
7 ferals
Vrasku
11 Crossbowmen
This list wouldn't be most people's first choice but I promise you it will beat the vast majority of armies out there. I entered it into two tournaments in the GBHL this year so was facing some of the the cheesiest and nastiest builds out there and it managed to win 1 tourney and come 2nd in another losing 1 out of 12 games in the process.
Feral Uruk hai are point for point the best troops in the game. I may have said this before
