Okay so this tooltip needs to be rewritten. As it stands it tells us:

"Delivers damage over time with a potency of 30 /70" Instead of:
"Delivers an attack with a potency of 30 / 70" like every other directional enhanced attack for PGL.

And secondly, it says "Delivers damage over time with a potency of 30 / 70 ... DURATION 18s" so again, the first line which says DoT instead of ATTACK also reaffirms itself as a DoT by giving a duration.

It should just read:

"Delivers an attack with a potency of 30 / 70.
Additional Effect: Damage over time: Potency 40"
Additional Effect: Greased Lightning
Additional Effect: Stance change thing."

So I don't need to stress about getting behind the mob for anything but bosses. I thought I was seriously gimping my levelling dps by not behind behind to get the stronger DoT. So long as the DoT is 40 front or back -- then I am happy (until the reword)