Your minions don't attack target if you hide behind a cover

If there's an obstacle between you and the target (e.g. a small non-traversable pillar), your minions don't attack the target, even if the target is clearly visible to the minions. In my case it was e.g. a Quadrilla boss and Skeletal Arsonist minions. Happens with other enemies and obstacles as well. The minions don't attack even if they stand right in the front of the enemy.