The ability lasts for 10 seconds again, but the damage is not restored:
8.1.0:
Path of Darkness:
This ability and its morphs now last 20 seconds, up from 10.
These abilities now tick once every 2 seconds, instead of once per second. They now apply their effects instantly, rather than after a delay.
Twisting Path (morph): Reduced the damage per tick of this morph by approximately 29%.
Refreshing Path (morph): Reduced the healing per tick by approximately 3%.
8.1.2:
Path of Darkness: Returned the duration and tick rate of this ability and its morphs to 10 seconds and 1 second, rather than 20 seconds and 2 seconds.
Twisting Path (morph): Reduced the cost to 2700, down from 3510.
So if you look at the table you will see in what a sad position the ability is in on PTS