I did some more testing just to make sure i'm not crazy on a 6mil, solo parse regarding twilight tormentor enrage
if anyone is wondering why i'm checking on the 6mil and not the 21m, the answer is time and pots
if i see anything worth investigating i'll definately check it on the 21m, but in the mean time i'm saving myself time and gold
Without enrage - 43k dps

With enrage - 43k dps

without enrage the twilight did 2.8k dps
with enrage it did 3k dps.
it was enraged for 49% of the fight, which is close enough to optimal. using any other damage skill instead of enrage will equate to an equal amount of dps increase, I recommend only using the enrage while you're in a mechanics cool down like changing positions or waiting for a boss mechanic to end / start.
TL;DR The ability is trash, ignore it once the fight starts.