You mean normal mode. You cleared normal mode.
Which is heroic mode.
You keep phrasing it as "second-highest difficulty", almost conspicuously so. This is highly misleading because the difficulty differentiation has significantly changed over the years, and it's GROSSLY fallacious to try and match it.
The most egregious example would be someone who's cleared Molten Core complaining that "they used to do raiding at the highest difficulty level" (true - one raid difficulty was all there was, so it was also the highest) but can't raid "at the highest difficulty level" now (which is mythic). And however technically correct that kind of labeling may be, it's just, you know, TWO COMPLETELY DIFFERENT THINGS which are brought into ostensible equivocation purely by an intentional obscuring of differentiation.
Because you intentionally set yourself up to feel that way. You've moved from normal to heroic raiding. That is a step up. Present-day heroic is not the same as WotLK-era normal. Not even close. It's much more difficult. AND YOU MADE IT THERE.
Lamenting that you're still "at the second-highest difficulty" instead of celebrating that you're now a heroic raider is a choice you are making for yourself.
I think we've identified the crux of the issue here.
You're not sad you're "only" doing heroic - you're mad there's people doing bigger numbers than you.
And here's something to ponder: if you had the gear they do, you'd STILL find people doing bigger numbers than you. Because there's always someone. Someone with more time, more experience, more skill, a better PC, less familial obligations, a bigger bank account, a longer penis and probably a dog that loves them more, too.
That is a you problem - you're having trouble looking at your own performance in your own context, and are instead compelled to measure up against others. That's always going to cause issues, no matter how the raids are designed. You want to artificially level a playing field that is never going to be level, in order to bring other people down closer to your own personal level because you can't handle that someone is doing something better or more than you.
Get over it. That's the only way to solve this - not through design, but through attitude.