So I designed a list to try and explore interactions between the Witch King and Balrog but also want it to be semi competitive. Below is my 800 list. I’m definitely worried about the numbers but went with the Witch King being a big hitter rather than full on support with more troops. How would you build a list with the Witch King and Balrog?

Moria:
Balrog
18 goblins 12 with shields 6 with bows

Angmar:
Witch King on Fell beast with crown 3/16/3
11 orcs with shield
1 orc with spear/shield
1 orc with banner and shield
2 specters
3 wild wargs

800 points with 38 model count and 3 might

Ok, i like your lust e lot ♡, but you are correct that the numbers are too few - 800p games are gigantic. So, how to improve?

I guess one strategy would be to think how to make witch king and balrog support each others? Tbh balrog does not need magical support.
With these setttings your wk and balrog cost together like 560/800. So getting a few orcs will just make u break fast. So i think something else should be figured out. One idea i have is u could try to build the rest of the army mobile, and let balrog go sort of alone. That would force an enemy to face ur balrog first, and then later in the game when balrog has already caused a lot dmg, the extra mobility could become useful as ur army could fast emerge, take objects and so on. But this strategy would probably benefit more from another wraith than WK, like maybe tainted? But i suppose u want wk because of the tittle so lets keep him... Maybe wild wargs instead of orcs so they are fast in the late game? With only 240 points of units u are anyways not necessarily going to need a banner, which makes imo wargs about as good as orcs without banners. Also at least i like wargs aesthetically and they are a bit more rare to face! Please let me know how u think about the next army list:

Moria-Angmar 796p, 26 units, 5 might:
*Balrog
*Witch King (3M-16W-3F) with crown on fb
-11 wild wargs
*Wild warg chieftain
-12 wild wargs