So I did some testing on abs and duration. Let's just say we need someone wiser to me to get anything concrete haha!
So @2100 jp you have a base dark skill of 469 I will write down a few tested items/sets.
status ....................skill stats time
naked.................... 469 +22 2:54
Erra....................... 479 +23 2:55
Kishar.................... 469 +22 3:10
Chupa.................... 469 +24 3:33
af+3...................... 490 +22 3:37
erra+chupa+kish.... 479 +25 3:53
chup+af3............... 490 +24 4:14
kish+err+chup+af3 500 +25 4:36
duration+skillgear... 562 +25 4:56
taking out the duration gear to see effect of dark skill
status ............. skill stats time
naked............. 469 +22 2:54
dark earring.... 472 +22 2:54
Casso+D.ear... 477 +22 2:54
casso+ear+leg 497 +22 2:59
---------------- 501 +22 3:00
---------------- 522 +22 3:04
---------------- 546 +22 3:10
pavor.............. 556 +24 3:13
---------------- 560 +22 3:13
so 91 skill gives +19 sec, its close to 5skill/sec but not spot on.
times are taken off timestamp, so give it an error of 1 sec. Regardless I think its overly clear that stacking dark skill past your "normal" skill gear is near pointless. Below is my set which gets me 563 skill +27 stats and 4:57 time, basically to hit that 5 min mark I want it would not really be worthwhile, not including black gear.
ItemSet 349381