I still haven't setup my screencapture stuff Azagarth. Also my nin sets still lacking and I'm still not master. I have taken a liking to triboxing VD Leviathan on NIN though, as well as VD AA GK. It's also pretty easy to DD a lot of T1 reisenjima as NIN. Not sure any of that is what you're looking for though.
I will say this, with enough attack buffs, Shun -> Ten -> Kamu -> Shun -> Shun will take about 52% of Leviathan's HP. Whether you get to do that or not depends entirely on Leviathan's random choices on TP moves. If it does Waterja, Tidal Wave, Poisonga, or Grand Fall you have to stop your chain to reapply Utsusemi or Miga or Both. Flood II, Spring Water, Spinning Dive, Water V etc all your friend. Sometimes it will do Grand Fall -> Grand Fall -> Waterja -> Grand Fall just to really upset your day. I've taken to just going into a full DT set if Miga is down for maximum consistency and safety as sometimes you hit your DT set before grand fall goes off but due to network lag end up taking it in your tp set and get one shot.
Whether NIN could solo this with just trusts or not would depend entirely on if you could find a way to keep a RDM trust alive, which I never could. They don't stand back far enough to be free from waterja, and a tidal wave -> waterja combo is dangerous. So I do tribox now :( Entrust haste will last pretty mucht he entire fight even if your geo dies, but sometimes it doesn't and I have to recast it (I reset it with Random Deal before I go in). So here's my NIN Tribox setup if you care to see it:
NIN - Yonin, Gakka, Utsusemi: San, Myoshu, Kakka, Berserk, Miga
GEO - Indi-Vex, Entrust Indi-Haste, Blaze Ecliptic Dematerialize Life Cycle Geo-Fury, Dia II
COR - Crooked Samurai Roll, Magus Roll
Qultada - Light Shots, Chaos, Fighters
Apururu - WHMing
Brygid - More safety
Qultada often dies but his rolls are long enough to still be useful, and incoming morbid sentiment, it's probably better if he does then he won't override your DD rolls with evokers or mess up skillchains with savage blade. If WHM dies it's game over so you have to both position her right and stagger your procs (blue, yellow, red) in order to give Apu enough time to pro/shell entire party and run off make sure she is not behind you to avoid dying to waterja also try to use some height advantage having her either higher or lower than you.
If miga wears stay in full DT set. Especially triboxing your reaction times won't always be good enough.
Proccing has to occur while leviathan is mid tp move or it won't do anything:
Yellow: Dia II or Yurin:Ichi
Blue: Provoke, I do this first as I run in, Levi doesn't always start a tp move at the start if he doesn't wait to use voke till you see the action lines around him.
Red: WS, usually after Blue, then 2-3 seconds pass and do Yellow, I"ll let 2-3 seconds pass and use WS for red. This is more than enough time to let apu do her stuff.
Shun will do about 3-5k if yellow proc isn't done but if yellow proc is done it will do about 8-14k. Radiance can do over 33k with a 5 step chain. With sam roll and daken your TP gain is almost faster than you can use it sometimes, especially if reapplying utsusemi/miga.
Unless SE gives a survivable Haste II trust and Bard then I don't see this fight as easily soloable in any short period of time on NIN, at least not consistently. Recasts are life for a NIN and without them, Miga rarely up, and even San and Ni can both be down at the same time and apu doesn't cure fast enough sometimes to let you live through 2-3 grand falls or waterjas in a row unless at least one of them was Miga'd. Triboxing or dualboxing it is really doable tho, as with most DD so this post isn't too special but figured I'd share anyway since you wanted people doing stuff with aeonics on NIN.