What is a shaman energetically?

Energetically, a shaman is a nugget.

 When you look at human energy, what you see is that nice big shape with all that stuff roiling inside and all the areas of a person's energy and all the lines that go together to make them up.  But when you look at a shaman who's about ready to go, you don't see the bubble anymore.  All you see is a nugget.  Everything else has been erased - everything else is gone.  There's just a nugget and one line that carries them into the center of creation.  Where they go?  I don't know.  I don't know any that have ever come back.  Maybe it's just another foolish way to die.

So isn't shamanism really about intent?

You're correct; it is all about intent when you get right down to it.  Intent is always something that is hard to grasp in some ways, but it's all a learning process after all.  I certainly haven't stopped learning.