Almost. If Player A (5TP/hit dagger) and Player B (25TP/hit gun) both have 0 Subtle Blow, then the Gun will give less TP to the mob over time. If they both have max Subtle Blow, the Gun will still give less TP to the mob over time. Adding Subtle Blow does not make the gun suddenly give less TP than the dagger with the same subtle blow, it always gave less TP to begin with.
To be honest, giving Subtle Blow to Ranger and not to Thief is completely rediculous. The fact that Monk, Dancer and Ninja, the other three low-delay 2-hit per round (DW or H2H) jobs get it and thief doesn't is stupid.
I'm not saying it's bad that Ranger gets it. I'm saying it's stupid that they got it over Thief. But then again, everyone seems to be getting shit over thief. Thief's Force critical ability? Meh, give it to Dnc and War too. Thf's enmity transfer? Can give that to Drg and Rng np. Thief's triple attack? Give it to Dnc, it's cool.