So now we know, 5-hit reaches 100% faster with proper set-up. So it's essentially a 6-hit with a really overpowered 6th hit. Is that clear?
Look, I'll do the easy part for you - the time to 100 tp. As we have been saying, 6-hit with proper buffs will WS faster than a 5-hit. Let's define proper buffs as Hasso, Marchx2, and Haste spell (total of 10+21+15 = 46% Haste). Let's say the 6-hit has 25% Haste from /DRG (Total 71% Haste) and the 5-hit has 12% Haste (Total 58% Haste). Assume both use Hagun (7.5 seconds per hit before Haste).
For the 6-hit, delay per swing is (7.5 seconds * 0.29) = 2.175 seconds
For the 5-hit, delay per swing is (7.5 seconds * 0.58) = 3.15 seconds
Let's say neither wears any Haste gear on their WS. Thus after the WS, they both have only 46% haste from buffs. This swing will have a delay of 7.5 seconds * 0.54 = 4.05 seconds.
OK, sum it all up:
6-hitter has WS(swing 1)->swing 2 + Swing 2->3, 3->4, 4->5, 5->6
= 4.05 + 4 * 2.175 seconds = 12.75 seconds
5-hitter has WS(swing 1)->swing 2 + Swing 2->3, 3->4, 4->5
= 4.05 + 3 * 3.15 seconds = 13.5 seconds
So the 6-hitter hits 100 TP in 12.75 seconds, and the 5-hitter in 13.5 seconds. The actual numbers may vary depending on how the game rounds haste and delay, but the end result should be the same. Now, remember that the 5-hitter is having to sacrifice some STR on the WS for Store TP. Thus, the 6-hitter should be having higher average WS's. Also, remember that the 6-hitter is hitting once more in the time to 100 tp. I don't care how much "like a truck" the 5-hitter hits for, they aren't making up for the extra damage of the 6-hitters extra swing. So, the 5-hitter should be losing on regular melee swing damage and on WS damage.
Now, you contend that SC damage really adds up to a lot. Well, since we have seen that the 6-hitter can WS faster, they should be more able to SC if so desired.
PS - I might have made an error in calculating this stuff. I'm not one of the math whizzes on the boards here, but I tried.