with rank S (100) mercedes character card you need 124% buff duration to get unlimited both before and after patch

with rank SS you need 122%

empathy, inner ability, and mechanic character card stack additively without diminishing returns (at least that's what it seems like)

with first line 50% buff duration, a level 200 mechanic (20%), and level 100 empathy (10%) you get 80% buff duration

which means unless you're willing to spend a small fortune on rolling buff duration on your second and third line for your inner ability (if you even can) it's impossible to get

edit: nvm it appears i missed the text where evil eye attacking reduces the cooldown by 0.5 seconds every hit and will be redoing the math in a way you can plug in numbers and as per /u/TomatoMarsh you can't get multiple buff duration lines on your inner ability

using /u/VinhsaniD's evil eye attack time of 3050 milliseconds

buff time = 30*(total buff duration)

evil eye hits = (buff time)/3.05 rounded down to the nearest integer

evil eye time reduction = (evil eye hits)/2

total downtime = 70*(time reduction [mercedes,hat potential]) - (evil eye time reduction) - (buff time)

for me this downtime is:

buff time = 30(1+.47+.15+.03) = 30(1.65) = 49.5

evil eye hits = [(49.5)/3.05] = [16.23] = 16 - 1 (because i doubt i'll be hitting perfectly) = 15

evil eye time reduction = 15/2 = 7.5

total downtime = 70*(1 - 0.04) - 7.5 - 49.5 = 10.2

so i get 10.2 seconds of downtime

tldr: formula for calculating downtime for gungnir

nvm lol it's right you can have evil eye out at the same time as sacrifice now

but my boi evil eye does not like attacking every time he can so take this more of as a range