yeah i cant see anywhere that minhiriath had around 5000 at the time of TA, must have read something similar when i was trying to decide if they were good or evil..
Anyway, i agree with you that they are just as relevant as Bree and W needs more evil presence, how about making them 'hording'? or make an orcish/goblin faction all over the W part of the map hording? both make more sense than a new 'power' in the west.
Its true the rangers were keeping evil at bay in the W but that no way means a 'powerful' evil faction should be there (powerful in regards to holding provinces like a foothold).
actually i really like the idea of a roaming orcish 'horde' faction, maybe they can be the rebel faction and we add a 'bandit' faction to hold the random settlements.
too many ideas for one post i think..