On a modded play through, I had a companion with this spell from level 1.
This meant I quickly learned the do's and don'ts of this spell.
I found it best used as a fight opener. I would sneak / invis into a group of enemies, and ensure my party was far enough away so as to avoid the spell.
Once casted, my party would join the caster and most/all enemies were knocked down with a few poisoned.
The only other spell with this amount of cheese was Chain Lightning + Rain (used in a similar fashion).
It is NOT a spell to be used once combat is engaged, unless you've positioned your party correctly which is likely a waste of AP at that point.
