I'm not sure what sort of ranged weapons the aztec's/Inca's historically used, but they might have some interesting throwing weapons for flavor.
As for the damage, it's a D3 which can be doubled with minimum unit size being 10 of which half attacks hit and half the hits wound. They'l be reliably doing quite a lot of damage. On top of that they have decent melee cabilities, and they are firly sturdy with 2 wounds and a 4+ save and rend protection. They're going to be both difficult to kill, and put out quite a lot of damage. It's that they don't have rend or mortal wounds, so they won't perform that well against armoured opponents, but they'l kill rapidly.
Also, can we remake rend protection to just be "reduces rend by x amount" instead of this weird mechanic we now have where it protects only against specific values of rend, but if the opponent has better rend the entire protection is lost.
Edit:
By the way, the likelyhood of a attack that deals 6 damage is:
10 * 0.5 * 1/6th * 1/3th = 10/18 = 5/9 =0.55555555, so just a bit more frequent than every other round you'd get an attack that deals 6 damage. On average a 10-model unit would deal about 6-7 wounds with their bows per round assuming no saves. With saves it gets a bit messy to calculate since the save could be Lucky and save the attack that deals 6 wounds, or save the attack that does only 1.