There actually isn't any instance where you should be playing NIN where it's correct to sub anything other than WAR. Unless of course you like being inefficient and terrible at FFXI.
It's funny you say this since it's the right answer.
If you need TH play THF. Anything else you could gain from a sub other than WAR is stupid. /DNC? Really? What for? a WHM or RDM or SCH or BRD mule/friend does more than /dnc, and it even lets you use the better DD sub, WAR, so you can do whatever it is your were doing better and faster.
BLU and SAM both give less than WAR sub from a damage dealing perspective, which is all that matters for a good ninjas subjob. It's especially funny that you would waste so much time keeping cocoon up instead of just having a PDT set. Cocoon is just a defense buff anyway, which is basically useless, and if it mattered at all guess what- /WAR has defender you could use when your shadows go down and ississikinini whatever isn't up.
lol.....
Real Katanas gain TP just as fast/faster than an oat 2-4 katana because of the way dual wield lowers TP gain.
Also, 15 stp from /sam is basically reducing the attack rounds required to hit 100 tp by 1, but guess what, the 10% DA from /war does exactly the same thing, except you gain the damage from 2 extra attacks instead of just gaining the TP from them. /WAR also gives you attack bonus JTs and berserk, but whatever, I doubt you listen to any of this anyway.
Meleeing yields more damage than casting crappy spells no matter what you do.
If your mages aren't hasting you in VW, you should tell them to quit sucking and do it.
Fast cast isn't useful because you shouldn't be casting unless it's for a proc that the BLMs or BLUs will call out for you.