As Cuba alredy said and many others before, if something is not working, change it. Obviously your tactic against the orcs is bad if you always end up with all the shields destroyed. Use nets, dogs, more archers xbowmen, throwing weaponry.
The mission with the orcs you had was an event mission with a spin, a very nice one. Fairly easy and tonns of loot.
If you struggle with the game or how to lvl and perk up your guys I suggest you search the forums for topics with some help. You can find the very basics in the link below.