TP return depends on Delay of your weapon. Higher delay gives more TP return, lower delay gives less TP return. Most Great Katana are 450 Delay, all the recommended ones are 450 except for relic Amanomurakumo.
For a 75 SAM to get 100% TP in 6 hits with a 450 Delay weapon you need +46 Store TP. At level 70 SAM get Job Trait Store TP of +25, which means we need +21 more in gear and merits to get this setup. +10 from 5 merits, +1 from brutal, +5 Rajas Ring are the usual cases needing 5 more. The last piece of gear to get store TP is usually from the feet or hands. +8 (9) Hachiman Kote (+1), +5 (6) Hachiman Sune-ate (+1) or +7 Usukane Sune-ate depending on what kind of setup you want.
Why get 6-hit setup? Well faster TP is either faster WS or strong WS with more TP. In 90 turns of attack after a WS and spamming WS whenever possible assuming no misses. 7-hit setup would get 15 WS while a 6-hit will get 18.
Lets use my equipment for example, Hachiman Kote +1 vs Ochiudo’s Kote.†If I do an average of only 400 damage per WS which is very low this 6-hit setup would yield me +1200 damage difference. To compare we look at how Ochiudo’s Kote compares to Hachiman Kote +1 in those 90 hits of melee hit.
5 STR vs 20 Attack – From my STR vs Attack for melee hits I can see 5 STR will increase my max damage by about 1 point while 20 Attack will increase my min and max damage by about 6 points. Which means my median will increase by 5.5 points of damage for the 90 hits.¬† Which will yield me 5.5 x 90 = 495 damage more with Ochiudo’s Kote.
So even if I hit as low as 400 damage per WS in only 90 hits the difference is 495 vs 1200. This is an understatement; in a merit PT with BRD I average 800+ per WS on parser, which would be 495 vs 2400 difference.
6-hit is very powerful for merit parties. It may be arguable for non-merit situations, but for stronger monsters I still spam when TA is not up and WS with TA when its up, the hate usually can balance out so it’s not a problem.