Okay...
You said this affects a huge proportion of the playerbase. Issues such as balancing don't matter outside of the highest level of content. As long as you understand the basics of your job and can get some mechanics down, you're good to go with most high-end content. It certainly doesn't affect most casual players because the content they engage with is clearable with only a very basic understanding of your job, and you can easily be carried through most of the content.
In your link, he says that 50% of players have some kind of engagement with high-end content, but clarifies that a lot of this is casual engagement such as just giving it a go, being invited (probably referring to FC's asking if they want to run some duty or trial), or having their FC help them with a drop. He also clarifies that of this it's around 30% who are clearing high-end content, a number which gives you a better idea of broader participation. If only 30% of players are clearing high end content, then the number of players at the highest level, and who could argue are affected by minor balancing differences, isn't going to be that high.
Also, when you consider our FC and pretty much every FC in the game, routinely helps players clear a high end trials or dutys for a drop, and thats the only high end content they ever touch, even the the clear number is skewed somewhat (potentially by a heck of a lot of he is including the Primal Trials in that number).
TLDR; You cannot include casual or one time content engagement in your "2% balancing difference" affects a huge amount of the playerbase argument; and a 50% casual content participation doesn't make a majority of players hardcore raiders.