gmoto, I have read her ultimate wich means she can be run in other decks excluding wolfs/werewolfs. Her werewolf side is the better side. Without putting situational in play, lets see what happens when she first comes into play and dies compared to the other
planeswalkers in the set. She either puts out a 2/2 token or gives a creature +2 +2 and vigilance for 4 drop. Jace is 5 and either gives card advantage or creature removal with a bounce. Sorin gives a card draw advantage with possible life loss or does max 6 damage to target creature/planswalker and life gain all for 6 drop. Nahiri is 4 drop and helps delirium and exiles something tapped.
With either of those 3 being dropped and dying you get more value from then arlinn
From that, her 'efficacy curve' is just steeper. While her early abilities lack luster, the endgame is devastating.
Discarding her because "dies to removal" is far too simplistic.