For Benthic:
-----------------MobA------------------
-----------------You-------------------
-----------------MobB------------------
-----------------MobC------------------
-----------------MobD------------------
Situation1: If you
face MobA and
cast on MobA it will only hit Mob A.
Situation 2: If you
face mob A and
cast on mob B, it will hit mob MobA, MobB, MobC and MobD.
Situation 3: If you
face MobB and
cast on MobB, it will hit MobB,MobC,MobD.
Situation 4: If you face MobB and cast on Mob A, it will hit MobB, MobC, MobD and MobA.
At least this is how I remember it.