Just got 550 JP on RDM and here is some testing I did with a friend in ballista
Target
Target MND: 173
No buffs, debuffs, was a COR/WHM
603 evasion
Myself RDM/SCH with Composure Gain-MND up
MND: 319
Emp 119 Body, Uk feet
504 Enfeebling Skill
521 evasion remaining, effect was -82
Saboteur With 119 Emp Body, 119 Emp Hands and Uk feet
403 evasion remaining, effect was -200
Emp 119 Body, Artifact 119 feet
521 evasion remaining, effect was -82 (For distract III Emp body and Uk feet don't stack).
Count's Garb, Artifact 119 feet
531 evasion remaining, effect was -72 (I think this is the cap for just dMND)
The -200 evasion test had Sab Distract III last 5 minutes and 20 seconds, so it might be possible to keep it on full time if no resists.
Can confirm that Inundation was +50% SC damage on Lights and Darkness's and I had zero issue landing it on anything.