The Advanced Class Guide says, concerning the barbarian level requirements to chose certain rage powers:
"The skald uses his skald level as his barbarian level
for the purpose of selecting rage powers that require a
minimum barbarian level"
But some rage powers like Elemental Blood or some feats like Extra Rage or Extra rage power don't seem to recognize the skald levels as barbarian levels like they should.
For the feats there is a workaround using the home rules but it doesn't work for the rage powers..