Did they run out of real Native Americans to play the role?
It's so weird, this idea that only Hollywood superstars can play a role, they just have to:
*gain 100 pounds
*put on a funny nose
*lose 50 pounds
*paint their face black.

I think Depp is a great actor, but I don't need to see him in everything. I even think he's miscast in Dark Shadows.