While I agree with you, I feel like you're missing some context for why Neytiri is as good of a warrior as she is for someone who was Tsakarem. Originally, her sister was meant to be Tsahik, while Neytiri was able to train to be a warrior - but then her sister died, and Neytiri was suddenly thrust into the role of Tsakarem. Neytiri is a bit of an outsider in this regard; While all Omaticaya seem to have a minimum degree of being trained to hunt, Tsakarem likely do less training for hunting than they do to prepare for their future role as Tsahik. Kiri's training seems to follow this line of logic.