^^^
Dual Wield Gear almost always wins on Ninja in any case where you're not running against delay reduction cap. Iga Zukin is especially potent because it gives a lot of haste and dual wield on the same piece so it's pretty much irreplaceable for low-buffs TPing.
Also yeah, that's pretty much the best set you can get. The best stuff for NIN TPing is relatively cheap aside from the Tenryu Tekko +1.
I only have 1 suggestion if my math is correct.
The Double March TP Set that you listed appears to have 27% haste when you only need 23% to cap delay reduction?
Why not swap out Tenryu Tekko+1 for Usukane Gote+1.
Then swap out Usukane Sune-Ate+1 for Thaumas Nails.
That would give you 24% haste which would still cap delay reduction and give you an extra additional 4~5% Double Attack depending on the Tenryu Tekko+1 augment.
Is the stp+9 on Usukane Sune-Ate+1 too important to sacrifice for the extra Double Attack?
The double march TP I posted does overshoot the haste, but I can't think of anything atm that would suitably let you drop the correct amount of haste in compensation for some better stats.
If you swap out Usk. Sune-Ate +1 and the Tenryu Tekko +1, you'll end up with 20% haste in gear (Lose 4% from Tekko, 3% from Boots). Even if the haste wasn't an issue though, the STP+9 does help a lot, yeah (Drops two hits to 100%), and extra acc/atk is always nice for high level stuff.
Tangentially related, as far as Usukane+1 VS Tenryu+1 for the extra 1% DA, it's basically the same deal as with MNK, where the Usukane +1 will win if you cap attack, but that is almost never going to happen. Worth noting if you ever get a ton of attack buffs though, I suppose.