Batum has an above average PER.
HOWEVER:
He has never averaged starters minutes. 30 minutes per game.
When Nik has a full season under his belt averaging 35+ minutes per game AND his PER is still well north of 15, then we can confidently label him "Above Average".
Right now I think he is about average.
Compare Batum to a player often mentioned on this board who has a similar PER - Andre Iguodala.
He has averaged 38 minutes per game for his freakin career.
THAT is a starter. And that is a player you can cofidently say is "above average". Nik still has to grow as a player.