hi guys, could you take a look at my army list and give me your thoughts? thanks in advance.

-warband 1
Morannon orc captain + shield
5 orcs + shield
4 orcs + spear + shield
2 orc trackers
-warband 2
Morannon orc captain+ shield
5 orcs + shield
4 orcs + spear + shield
2 orc trackers
-warband 3
Captain of the black guard
8 black guard of Barad-Dûr
-warband 4
Mordor troll chieftain
5 orcs + shield
4 orcs + spear + shield
2 orc trackers

notes:
-Orc archers, even trackers, don't seem that good to me, would it be viable to swap them for more infantry?
-My friend mainly plays rohan, is it a good idea to swap my troll (or something else) for morgul knights?

A few comments:
A good start, a troll chief is pretty good at that point level, but I think a wraith might serve you better.
Orc bows do suck, but if your friend plays Rohan and runs around shooting and never charging in, you'll need something to unhorse him.
As for the Knights, you don't need to counter cavalry with cavalry, against Rohan 2 orcs with spears are usually enough. You might be better off keeping your numbers high. That said, Knights combined with a wraith (for the terror bubble) are difficult to charge and can pick their targets more effectively.

I feel like i would be inclined to drop some of your captains for Shagrat war leader and or a named wraith, probably shadow lord, maybe on a fell beast? I feel like i would take morannon orcs too not just the captains. I'd definitely consider fury too.

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Cheers,

P

And how many models will be left after this? Maybe 35 this is far too low.
But you could take a miniringwraith with about 2/0/1 which would be about 20 points more than an captain.

first of all thanks for the comments. I will definatly try to include a nazgul in my next list. I have the betrayer and the knight of umbar at my disposal, which do you think would be better suited?