Samurai is a selfish job. rDPS is largely irrelevant to use as a solo metric for it. You need to look at aDPS, rDPS and how much damage it does under raid buffs. The latter is especially important.
This video explains it far better but he highlights the difference between Warrior and Dark Knight and why the latter is overwhelmingly better. Under raid buffs, Dark Knight contributes nearly 1,200 rDPS under buffs whereas Warrior only contributes 500. Hence the gap between them is far higher than the 350 difference the rDPS tab suggestions. Their respective aDPS shows a
staggering 700 difference.
All this aside, if you look at the speed meta, Samurai completely dominates with a whooping 36.4% amongst Melee in P1S.
When factoring in everything above, Samurai is, indeed, the strongest DPS since 6.08. Black Mage is competitive with it as are Ninja and Dragoon.