[Manuk]

Useless is not to be a light unit. useless is to be another better unit so it make the first unit redundant.
It´s always better to recruit tribal shortbows intead of generic ones because they cost 8g intead of 10g and cost less resources, and have map movement 2 instead of 1, and they have a bonus dependant on the tribe (deer tribe have better defense).
other tribesmen are ok if you have a sudden war and are in need of some bulk force. low resource and special ability like if you mass the guys with two daggers cover the battle front filling the gaps between your heavy elites and delivering 2 attacks to lessen the defense thanks to multiple attacks effect.
bear tribe javeliners have extra strenght and this means more range of throw and more damage to hand to hand.
on the other hand light cavarly archers are a little crappy.
but normal light cavalry can buy you quick flankers.
I often overlook recruiting barbarians because of they high cost and little survability. so of indt units i find them to be near the worst units.