College of the Hoop Bard subclass
by Marc Saindonone thing over-simplification I see in Atruaghin is that 'since they are low-tech, they are Barbarians', yet strangely the Norse berserker frenzied warrior has very little in common to most of the tribes, as the Children of Atruaghin have more in common Ethengarian raiders (with the optional 'community wealth' presented in their gazetteer). Sure 'Path of the Totem Warrior' Barbarian has totem in its name, but that's just about it.
Instead of looking to the Barbarian for inspiration for the Atruaghin, perhaps the Bard makes a better option, with the 'College of the Hoop' (placeholder name) serving as one of the main wheels that keep the Children of the Horse going as a tribe federation (the other being the Fighter - akin to the Comanche Dog Soldier - and the 'Shamani' sort of Cleric/Druid). The Children of the Horse are warriors foremost, but 'plateau-locked' for centuries, which prevents them from gaining the most out of raiding (unless you integrate my idea that they have pegasi mustangs and thunderbirds to raid into Sind and Darokin) . So I guess they must be putting their energies elsewhere, notably in artistic performance and creation, to keep themselves busy and to preserve the tales of ancient warriors to keep their culture alive.
(pic from: Native American Hoop Dance)