Actually there IS an arrow that indicates the monster's facing which direction.
Below monster, on the ground, there's a red ring.
This red ring will have an arrow pointing outwards, and that arrow is the direction the monster is facing.
One of my character is a lancer, and I use that arrow to judge if I am beside or behind a monster to use proper skill.
While majority of the monster is easy to know where's the head, I encountered some plant-like monster with tentacles and I can't tell where's the head, and can only rely on that red arrow on the ground.

This post has been edited by unknowngst: Aug 24 2013, 02:59 PM

Yupe. I always rely on the arrow.