Did you miss this while looking at yourself in the mirror? Maybe I should elaborate more for you. Killing AV using the Justice wall is an exploit. Why? Because SE fixed it shortly after. Using the properties of hate to your advantage is not, especially when SE hasn't changed hate for ages. People are recommending against it because people think the older way is better for some unbeknown reason or they did Divine Might the "harder way" a long time ago and feel others need to do it that way as well. My grandfather used horses, everyone should use horses too because that's how things were. Get with the times.
PLD/NIN is everything and more than PLD/WAR ever was. I would never dare to use /WAR over /NIN for sky gods, sea jailers (except for jol; /RDM), HNM, Assaults, Nyzul, Salvage, Limbus or meriting, there's no reason at all to sub WAR for any those. Awesome, you have Provoke every 30s, but it's a shame you shed hate fast taking hits. Unless of course, /NIN is an exploit and people should do it the old ways just because.
I would never dare to use in most of the situations you listed at all...
Sky gods: Kirin tanked fine /war or /nin, but with zerging the need for pld's is gone
Byakko: I tanked PLD/WAR a couple of weeks ago, it's fine
Suzy: NIN excels
Seiryu: PLD/NIN
Genbu: /WAR or /NIN work, just different strats for each
Sky gods is a wash
HNM:
Vrtra: If not zerging, /war is a sufficient tank. /NIN works as well, but requires more support
Tiamat/Jorm: NIN's are more superior tanks, PLD can do it but I wouldn't choose it if other jobs available. But, you're right, if I did, /nin.
Toau HNM: /nin
Kings: /War for KB, /anything for NQ. /WAR or /NIN for aspid, /anything for nq
Faf/Nid: My favorite HNM to tank...and it's much more efficient with a WAR and NIN dual tank then pld/nins. Were I to use PLD tanks, then sure, /nin.
Other minor zilart HNM's - /war more than sufficient, /nin works, but why?
HNM again, a wash.
Assault:
I haven't seen ONE assault where PLD/NIN would be useful. Not one. In all my assault experience, I've gone PLD TWICE...and it was /war once to hold hate on multiple mobs, /whm on the other so I could erase myself while kiting.
Nyzul: No experience here, you may have me, you may not.
Salvage: We have 4 people with PLD 75 in our Salvage shell, have a very high success rate. Times we've had anyone come PLD: 0 Can't help you here.
Limbus: Ultima / Omega /nin, farming sessions /war (preferably other job)
I'll give you a wash even though a vast majority of the time would be /war.
Meriting: Are you serious? PLD is a leech in merits no matter what the sj. Ultimately geared, a PLD can hold his own with a decently geared Dmg class job, but come on. The majority of invites the majority of the playerbase will get are going to be traditional style parties...and /war.
EXP 1-75: /war
The reason SE can't 'fix' this exploit is because they haven't found a way yet to do it. They want to keep the integrity of proper uses (allowing pets to get hate) but haven't found a way to do that without changing hate altogether. It's an acceptable fact, but still an exploit of game mechanics.