I had an idea of abusing Nightblade with Perfect agony, so I did a bit of PoB (the real game as someone call it), and got some nice results.

This is offcourse not a full build, so the 2c budget might be a bit misleading, but the point is that the items that will get this build going will cost you that much (Bino's and Ungil's)

https://pastebin.com/zR4JS5cS

Some maths about elusive and nightblade: We have 200% elusive from nightblade and ascendancy. That makes the crit multi from nightblade 280%. Elusive will degrade at a rate of 20% per second. This means that it will go down to 140% effectiveness before being refreshed (20% * 3 seconds withering step CD) so the halfway point is 170% effectiveness. 140*1.7=238% crit multi. With perfect agony that makes for 119% Dot Multi instead of the 140% dot multi that you would have at max elusive effectiveness. If you put a -21% dot multi in the PoB you will get closer to the actual DPS that night lade gives.

Edit: Added some more info about nightblade