7 to 6-hit is an ~14% increase to WS frequency(and subsequently WS damage), 7 to 5-hit is an ~29% increase. Whatever means to multi-attacks you're using must, on average, be at least equal to that increase to be better. This applies regardless of your subjob, but you should virtually always be /SAM, so 5-hit is more than attainable.
Slightly trickier than that, actually.
I set up drg/rdm in my spreadsheet so that I don't have any secondary effects from /sam or /war job traits. Used the gear set in the OP (using Gugnir 95), aside from the Moonshade (just used Aesir, there). That gives enough Store TP to end up with 14.6 TP during melee, 15.4 during WS, so a pretty clean 7-hit build.
With no outside buffs or debuffs, no jumps (because jumps affect the result in an indirect way), using Stardiver, and vs DC Dynamis mob, DPS is 115.878. Average rounds per weaponskill is 5.48.
Now I add 15 Store TP to TP and WS sets, putting TP per hit at 16.6/17.4 for an easy 6-hit. DPS is now 124.675 (7.6% increase), and average rounds per weaponskill is 4.72 (note: it's not a simple -1 to average rounds since multi-attacks influence the results).
Now, the same thing with Haste and Marches:
Base: 228.842
+15 STP: 244.198
A 6.7% increase (a lesser increase because of the fixed time of using the weaponskill itself while haste reduces melee time).
Now add jumps:
No haste:
Base: 145.946
+15 STP: 154.312
Gain 5.7%
Hasted:
Base: 253.376
+15 STP: 267.980
Gain 5.7%
Overall, dropping from a 7-hit to a 6-hit was only worth 6%-7% more DPS, rather than the theoretical 14%.
Try again, dropping to a 5-hit. Added 40 total arbitrary Store TP to make TP per hit 19.9/20.7. Average rounds per weaponskill: 3.95.
Comparison with same config, 7-hit:
No haste, no jumps: 137.073 (+18.3%)
Haste, no jumps: 265.458 (+16.0%)
No haste, jumps: 166.171 (+13.9%)
Haste, jumps: 288.266 (+13.8%)
Rather than the theoretical 29% increase.
Now, going back to the basic issue, set up a comparison for drg/sam. Used Bukhis target, Dia 2, Hasso and Haste as the basics for buff/debuff.
It's basically a natural 6-hit while /sam, so the only question would be the value of moving to a 5-hit. Unfortunately reaching a 5-hit isn't actually that great.
First, going from a 6-hit to a 5-hit using the bare minimum Store TP necessary to drop average rounds per weaponskill only drops avg rounds from 4.67 to 4.27. It takes a fair amount of Store TP above that to drop the average rounds just a bit at a time, and you end up with a net loss compared to the gear you're swapping out.
Second, you pretty quickly reach the limit of decent gear choices with any useful amount of Store TP for drg. That makes a 'good' 5-hit build rather difficult to achieve.
How much of a difference? Well the OP's gear set is at 170.954, while the 5-hit build is at 166.149, so the OP's build is 2.9% ahead. I can't say that my 5-hit is optimal, but it's the best I can come up with offhand (not including neo-Nyzul gear). If I use Phorcys head and legs, I can get the 5-hit build up to 169.889.
Side note on Porthos: Porthos looks like the best body possible when gearing for 6-hit, though using Phorcys head and/or legs can get the overall result fairly close when combined with Lancer+2 body. If anyone has a better setup to suggest, I'd be interested in looking at it.