This needs to be said

[Rilifane]

Good job balance is technically only important for week 1 raiders but in practice many more people will feel its lack. We've seen paladins get locked out of PFs back in asphodelos and while most of those PFs were out of their minds to lock paladin out of stuff like p1s and p2s, the image of good job balance is as important as good job balance itself. People who love playing paladin and warrior shouldnt have to feel like they are holding their party back specifically because of the job choice. That feeling has to be reserved for skill issues.

Adding to this some people seem to forget that balance still affects lower gameplay levels as well.
If a PLD is signifcantly behind DRK, he is at pretty much all gameplay levels. The average PLD is still weaker than the average DRK, not just the top-tier PLD weaker than the top-tier DRK. So the average player will also feel the lack of job balance; they reach the tight dps checks later and have gear to make up for their lack of skill compared to a top-tier group but they are still affected.
While the average PLD can just "git gud" and definitely has more to worry about than being inherently weaker it still doesn't change the fact that if a class is noticeably ahead, it is at all gameplay levels. Balance makes or breaks kills for week 1 raiders but it still trickles down into midcore/ casual statics as well.

I can see how it sounds, but their skill level probably did become good from repeating the content. They were probably doing it with a good job composition as well.

This is a good point. The people who get paid to play this game, mostly, are streamers and content creators. There isn't any magic about why they go around clearing savage and ultimate before everyone else, they just have more time to do it than most players who have to spend a lot of their time doing a job that isn't related to the game. Spending more time on the game usually translates to being better at it as well.

And that is a bigger problem than they gave it credit for.
I'm sorry but I struggle to believe that a party of experienced 1st week raiders that all sit around 99% uptime (or more), potted twice, have no deaths, no damage down, only minor rotational mistakes if any is so far behind in terms of gameplay that they can't clear the doorboss while the team from SE can; some of the first week logs that ended with wipe after wipe were amazing in terms of gameplay and they still failed because they had some classes that were simply too much behind others. Comp had to play a role in this.
Trying to to twist it into a "Guess we got too good" as the only reason won't work.