The SSS dummies certainly aren't the best meter but I think it's decent enough. Barely not clearing it with beginning of the season gear? I think you'll be fine. However, you have to also consider that we are near the end of the current tier. If you can't clear the v5s dummy in at least the 360 tome gear after all these weeks, crafted gear, Eureka gear, and what have you, then I think that's a good enough indicator that you need to go back to the lab and practice a new rotation with the class. There's enough resources out there to help buff you up. It's not the end of the world that you're not the best at something, but not doing anything to better yourself in content that "challenges you" will lead to more situations where people can't destroy the chimney in train.

You also have to remember that parses uploaded to the logs is not everyone in the game. That is more representative of the raiding community. In essence, your run is being compared to your fellow savage peers. You may be a king among casuals, but if you consistently get gray parses that doesn't mean you're trash. It means you're the bottom of most people doing endgame content, but even more than that, you're at the lower end of the spectrum of raiders that care enough to parse. If you have a low ilevel at the end of a tier, that could also be an influential factor.

There is always room for improvement. Getting bent out of shape over a few grays will do nobody good.