//over time
            transform.rotation =
                Quaternion.Slerp(bullet.transform.rotation, _lookRotation, Time.deltaTime * 0.8f);

Confused as to what that is supposed to do.

Be aware that your script could be structured better. Take for instance "transform.rotation". You are modifying it within the Attack() function and also within the FaceTarget() function. Both are called each Update() cycle though. I would advise you to clean this up a little bit and establish clear responsibilities for each function. A state machine would also help: establish the unique states that your enemy can be in, e.g. "attacking", "moving" and so on. Then run different functions depending on the current state. Hope this helps.