Palidan, it is clear that the Orc commander's objective is to smash the defences by direct assault. He is not trying to attrite you, nor trying to deceive. He has no 'elite' forces you can see, so his only good quality forces are the ones with swords and shileds rather than spears- a better equipment combination overall, especially for this kind of work. He has thrown them straight into the main assault and he is willing to let them die to carry the fight- that must be the main thrust.
Clearly the orc commander is a man with some battle sense, however, as he is keeping reserves and sending them out accordingly. His attacks on the west and east walls have been teasing- small forces advancing under heavy opposition. They are designed to distract you; to pull forces away from the main assault to give that a greater chance of success. The Orcs that have successfully mounted the Western Wall are not trying to penetrate further- they are moving to attack the defenders of the main assault.
The Orc commander does not know who and where you are- he is blind as to what goes on inside. But, he knows your forces on the Eastern wall, whatever they are, have been strong enough to resist him. The extra ten orcs he has sent that way are not meant to take the wall; he is trying to keep those forces stuck there to make sure they don't move elesewhere. He's sent those people to die. Meanwhile on the west he is reinforcing more heavily as he seeks to exploit the breakthrough.
However, he is not allowing this to distract him from his main assault, which is where the baulk of his reinforcements are going. If he was a bold and daring leader, he may have tried to let that assault burn out and instead shift his main attack to the west and take the fortress by escalade. He has not; you think there are several factors here. First, your opponent is not stupid but he shows no signs of genius either; his attack is very conventional- which makes it no less dangerous, but at least you are not worrying about sudden strokes of genius. He'll stick with his main plan; as said, the breakthrough in the west wall will be used to support his main thrust, not to take the fortress. Second, he probably doesn't know just quite how open the fortress actually is to the west right now.
Thirdly, and more tellingly, the Dunlendings- the way that group of ten just opportunistically wandered into the western wall fight; it seems they are not being well commanded- you think that the Orc commander has a relatively poor grasp over his Hillmen allies and they are not being focussed. He doesn't have enough control over his forces for a sharp change in strategy- that is good to know.
Baranar, meanwhile, has set up most of his forces to blunt the main assaults- they are ready in the courtyard below. He has left a skeleton staff manning the walls- he is gambling on holding off the Orc attacks there long enough to be able to destroy the main assaults then they come. You can see him now moving to prepare to repel the western attack- however, he is drawing off men from his main force to do that.
Baranar's plan is solid- if he can keep his forces ready to destroy the Orc's main assaults, then they have no other plan left. If they loose too many people in those assaults they won't be able to hold against the approaching army from Arthedain- they will withdraw.
The problem is, if the walls come under too much pressure and Baranar has to keep moving men to plug gaps, then he may not have enough force to repel the assaults- and the Fortress will fall.
That has to be your job, Palidan. You have to make Baranar's gamble hold- keep the walls secure and stop him having to deplete his main force. If you can keep him intact you will win.
Two other things you should note. First, the Orc commander is not committing all at once- you think he has a second assault ready to go after this one. And second... even that in mind, not enough is going on. You're missing something, Palidan- not everything about this fight is getting through to you.