The aoe red circle that these mobs do is either too small or the attack itself is too big. The attack that actually hits you is about 3-4 otter/papu sizes away from the actual red circle.

For example. The ranged attack from the ranged Papu/otters don't hit the Crab because you're too far away, but the crabs Melee aoe attack will hit you from your ranged position.