To me it is not about weak or strong factions made on purpose. What I am seeing is that the map design is what actually making some factions too strong and some other weak. Just compare the Khuzait map with NE map:
Khuzait:
Image Khuzait-Map hosted in ImgBB
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NE:
Image NE-Map hosted in ImgBB
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It is pretty clear why Khuzaits are able to recruit armies much faster than other factions. Just look how close fiefs are to each other and how easy to access and at the same time protected their fiefs are. Now check NE map, the best area for recruiting troops is Amprela, Syratos castle and Episona Castle, but these villages get constantly raided for Khuzaits pretty early and NE lose all its recruiting power pretty fast.
Plus the Khuzaits army composition is simply better, even removing cavalry bonus in simulated battles and Khuzaits cultural bonus, Khuzait lords are simply much faster and Khuzait map is pretty easy to defend and reirforcements can arrive pretty fast. Raiding the Khuzaits villages is almost an impossible task for NE lords because Khuzaits parties are just much faster and able to protect their villages pretty effectively.
So yes, some factions feel much stronger but I think that it was not a deliberated devs decision, but they understimated the potential of a good map position. Battania also has a great map and fiefs are pretty pretty close but I just have to change some few things to see Battania getting wrecked because they are pretty much surrounded by everyone, while Khuzaits are placed in a corner, have pretty close fiefs to each other, and have speed advantage... No much to do to fix this without making drastic changes IMO.