Dual Blades do their damage over the course of many attacks, so Razor Sharp will be a big skill to help with kill times. That said, your current set on the Rathalos S armor will probably net you faster times, since Speed Sharpening is almost as good and you also have AuL. Stamina is more used on the Dual Blades for the Demon Mode, which itself is used when you have large openings or the monster is exhausted, but a Mega Dash Juice can take care of most of your needs in both situations. With the Dios Slicers+ and your Rathalos S armor and a bit of practice, you can get sub 15 or even sub 10-minute kills on most monsters.
With Dual Blades in high rank, you want Razor Sharp or Speed Sharpening AND Attack Up (L) first and foremost. After you get those two you can go for utility stuff.
If you are set on running a stamina set, by all means stay with the Ludroth U. Try to gem in Speed Sharpening over Scavenger, as it will benefit you more in the long run and energy drinks are really easy to make. Scavenger basically makes you need half as many to get to max, meaning it is only useful at the very beginning of the life, whereas Speed Sharpening will allow you to spend less time in the entire fight resharpening and more time hitting the monster in question.
Half of the skills on the Agnaktor set are wasted if you only use the Dios Slicers, but the Salamanders DB are a pretty good fire weapon in high rank. Unfortunately, they get heavily outclassed when you graduate to G-rank.
My personal recommendation is to go with the Rathalos S set for faster quests, and the Ludroth U set for more enjoyment in your quests.
A final alternative is to make the Rath Soul set, which comes with Razor Sharp, Critical Eye 2, Earplugs, and an easily gemmed-out Health -10. With any kind of charm with Hearing or Expert, you can easily upgrade one or potentially both skills, and it becomes a really strong general-purpose set for the end of high rank and the beginning of G-rank.