This was one of those complaints/issues I didn't understand, but, they could've went a different route to still have them feel 'rare'; ie limit it to castle recruit (or town) only; not villages. Or, like they did with the bandit troops/perks with those restrictions. Whether you need a certain influence threshold to recruit nobles (or spend with that 'currency'), or apply some perk to get the upper most tier of the noble troop upgrades or some added/discount cost wage perk, etc...
Right now, they don't feel 'noble/unique/rare' enough, might as well be exactly the same as the rest of the faction troop tree; and less that 'challenge' in trying to get a full stack of noble troops which is very easy to do still and quickly.
The only way to get them before was transforming bandits, which lets be honest was ****ing stupid and made no sense that a noble troop line came only from bandits.
Also the current version gives more importance to owning castles as its only castle villages that provide noble troops.
I've done the analysis a few times and there is not a ton of noble troops in AI parties as they are not selective about recruiting troops, you see an AI party with 25 - 33% noble troops.
Using the player as a comparison is silly as the player will behave differently from the AI and can ignore recruiting normal troops and only recruit noble troops. Even when the only way to get noble troops was to recruit bandits, players still only focused on that. So making them more rare wont stop people from making fian only parties but will just lock out AI parties from ever having them.
Personally I want to fight against some noble troops, which the current system allows and the previous system didnt allow. If you dont want to have all noble troops then dont focus on just recruiting them, recruit from towns and town villages where they arent available.