That can be a real problem for tribes, I agree. In my youth I worked with an organization for Haudenosaunee cultural preservation in the US and while the politics are a lot different there the status of tribes as nations means that there are a lot of weird power dynamics.

In particular this organization was opposing considerations of the Mohawk People to invite in outside investors that wanted to build casinos on reservation land - that's a hard decision to make and even harder when there is a single ultimate tribal representative that you can throw ten million dollars at without serious impacting long term financial expectations. The Mohawk Council of Chiefs in Akwesasne[1] represents a tribe with enough members, and historical precedent, that they benefit from and enjoy an actual government body, but many of these tribes are small enough or remote enough that a single member is vested with a lot of power and this will often go poorly. I don't think there's a really clear good solution here - it'd probably make sense to consolidate tribes into fewer regional bands but Natives are obviously pretty skittish about surrendering any of what little power of self-governance they have.

1. http://www.akwesasne.ca/about/