One of the most annoying enemies in the game by far is the fairies. Not even because they are difficult, but because some giant enemy or swarm or hill will hide them and you constantly try to rotate around the swarm to eliminate a very threatening enemy.
Ever since the weapons patch, I'm also getting entire legions of fairies making a shield chain with each other, making them invincible.
And then there's cores taking the shield and protecting a shield fairy that protects them?
This is DEFINITELY not a good mechanic.