Gaah just lost my post so ill keep this short:
Your weakness is going to be magic defense and speed. By magic i mean those movement spells that will tend to get around your side and roll up a flank as you simply don't have enough units to make this a hard proposition. Also VC and TK will give this army fits as it doesn't have enough units to provide any type of a backfield to make things hard on the enemy.
By speed i simply mean that you can't possibly hope to hold up each flank with a chariot and a giant, both are fairly easily dispached (sic) and once they're gone that flanks gonna become a golden target for all enemy units with movement.
Now as to how to combat this, well i would suggest the following:
First replace one or both giants, they're fairly easy to knock off and are huge chunks of VP's in an army like this. If you do replace them i would suggest it be with something like this: 1 Giant= 2 Gobbo chariots, and a doom diver, 2 giants= 2 Orc chariots, 2 Doom Divers, and a chariot for the orc with the horn, also the unit that loses a Orc Character should get the 1 more model needed ot bring it up to size.
G\Drop the extra crew from each chariot and give the spider riders bows at least, thatll allow them to harass until they get to charge warmachines or whatever.
As stated before replace the Staff with 2 dispell scrolls for magic defense or, if you really really wanna cast spells with only one mage at least get the item that gives you +1 dice for EACH unit within 20 i think it was, just dont expect the shaman to survive as much.
Beyond that it looks feasible and good luck
