Such a ridiculous dead horse I may be beating with this. I apologize for asking a look over on this for like the 20th time so bear with me please. I wanted to confirm these sets for TP/Kaiten as optimal with the proper information described in their descriptions.
Melee TP
20.8 TP per hit, 25% Haste, Quadruple Attack+2%, Double Attack+8%, Accuracy+72, Attack+46 and Zanshin+60%. When Tachi: Kaiten aftermath is up the TP per hit is boosted to 21.6 (+7). The only upgrades even possible are
phos belt +1 to cap 25.9% Haste and
Tenryu tekko +1 with Double Attack+2% augment.
Kaiten
STR+56, Attack+153 and Accuracy+60. Tachi-Kaiten: 60% STR Modifier with an added 40% damage bonus from the 99 version's hidden effect. The weapon skill hit will return a value of 16.0 TP but activate the aftermath mentioned in the TP set. Only possible upgrades are
Tenryu hakama +1 with augment of weapon skill damage+3% and
Vulcan's pearl.
tank/pdt/ohshit
Damage Taken-18%, Physical Damage Taken-29% (Assuming -5% per Dark Ring and -1% per Darkness Earring), Occasionally annuls physical damage and Occasionally absorbs earth damage. Defense+264 and VIT+46 if you care about that as well. Combined total of -47% PDT. Only plausible upgrades are a
defending ring and slightly improved augments.
I used FFXI calc and all the information available on BG wiki as well as researched the previous pages of this thread in attempt to compile this data. If you could please fact check all data and see if I covered all possible upgrades. Let me know if there is something I missed or feel free to ask why I chose a certain piece if necessary. The five items I excluded (
Tenryu tekko +1,
Tenryu hakama +1,
phos belt +1,
flame pearl and
defending ring) I personally find extremely rare on Siren and are unrealistic at this time.