I have Haub/SH/AF, is the Double Attack worth upgrading a Haub to Aurore? I am assuming the Aurore is slightly better but not by that much, however I've been wrong before.
You're fine with Haub/AF, but replace the SH with Aurore.
- Hauby is still your best WS piece (though if you're capping Acc, Osode beats it, and eventually Iga+1/+2 trumps all). No real problem with WSing in Hauby all the way to Iga+1/+2 though.
- AF/AF+1 are still tops as TP body when you're capping Acc. At lv90 with capped Katana skill, Cruor buffs, and Razed Ruins atma, you'll almost certainly be capped on most things in Abyssea. Outside Abyssea, you'll be capped on lv75 era mobs just based on level correction - in general the only thing that's currently an issue are Voidwatch NMs.
- Aurore makes SH obsolete - it's a better solo choice (and at about the same price). Same evasion/accuracy (Aurore has DEX+4/AGI+4, equating to an extra 2 Acc/Eva), plus adds DA+2% and the benefits of raw STR/AGI/DEX. Some people might still prefer something like SH+1/Antares for slightly more Eva, I'd personally take the DA on Aurore (not to mention it's cheaper).
I have not finished CoP, are 2x Sniper's still decent enough?
If you're on the lower end of 75-90 and fighting higher level stuff in Abyssea, or significantly underleveled weapon skill, they can have some use. But as noted above, you'll be capping Acc on most things by lv90 so it's time to ditch Sniper's. With capped Acc, Sniper's are literally worse than having nothing at all on your fingers, since the Acc isn't doing anything for you and there are negative DEF/darkness resist stats.
Keen Ring is really cheap and has some nice Atk. Heed Ring is more expensive but is a great evasion piece with a big chunk of subtle blow - terrific solo choice and nice even in a group to reduce feeding TP to the mob (particularly important while trying to get !!! triggers in Abyssea, since a WS/spell during a mob's TP move won't proc !!!). The Acc on each is somewhat redundant, but doesn't hurt. ToAU isn't hard these days either, and Ulthalam's Ring is still a useful option. Iota can also make a decent placeholder if you already have it or have Einherjar points to burn, AGI/DEX are never a bad thing for a NIN.
I currently have Senj/Fudo. I am 85 but I will go 2x Ichi till I can get the others. Is Hiwa a decent option for OH or is the damage too low? I can't see dropping the extra crit of my current setup for it.
2x Ichi-an is fine to hold you over until you get the better R/E Katanas or magian stuff. You're almost to 87 to use Ichi-an, so I wouldn't really bother changing what you have until then as the difference would be fairly minor.
Another weapon tip - skill up dagger and Great Katana when you can, as they have WS that a NIN can use to trigger weaknesses on Abyssea NMs. Tachi: Jinpu and Tachi: Koki for GK (red weakness). Cyclone/Energy Drain (red), and Shadowstich/Evisceration (blue) for Dagger. Red is the weakness that you need to hit to get Atma, and to help for getting Key Items from NMs. In an Atma farming group, a NIN is highly desired since it's the only job that can use Blade: Ei (the only Katana WS that triggers red), and a NIN plus a WAR can hit every red !!! there is.