Is there a strict lore reason that there are no non-human bandits/ minor factions other than the usual deserters? Barombur talks about becoming a brigand after getting sick of extortionate taxes and the Geldar used to be a hostile minor faction.
Maybe something like:
-Renegade Dwarves; spawn in the Dwarfven mountains and hostile to everyone except the Mosoru and Perisno Adventurers with whom they have allied with against their Kaikoth overlords. Equipped with the low-end Dwarf cloth and leather armour, but with decent melee weapons and shields.
-Wandering Giants; spawn in and just outside Giant territory, these are scouting adventurers and hunters, with a fast travel speed on the map. Hostile to everyone except Sut and Bakhal, they have a mediocre selection of giant's armour, but are mostly armed with spears and bows, so are a threat to cavalry on the battlefield.
-Elintoran Guerrilla's; Basically the Socia'tiel, they are hostile to all factions hostile to Elintor, Elintor/ allied factions parties will assist them in battle, and they are hostile to non-elven player characters, except when allied to Elintor, as a vassal or merc. With mediocre to decent armour, good bows and amazing archery skills, they also include horse archers in their parties. Speedy on the map, shooty on the battlefield, you really don't want to face them with low-level troops. Pathfinding specialist.
Elven Foresters; Elves who have rejected the civilised ways of their Geldar and Elintoran brethren, they have returned to a more "natural" way of life in the forest. They are neutral to everyone except bandits/deserters, who see them as easy pickings and are hostile. They usually escape though, as they spawn in tiny groups with a fast map speed. They carry knives and wear only the weakest fur and cloth armour, but have decent bows and archery skills. Their parties also include female elves armed in a similar way; elven peasant women they have persuaded to join them in the forest in one way or another. Help them, leave them alone, or attack them to acquire a bow early in the game, your choice.