This is not true. I'm casual, taking my time working on t10, and these relic quests scare the shit out of me. Any1 doing these relic quests are in my eyes hardcore as it gets.

The ff14 community definition of hardcore confuses me a lot....
I can see why it confuses you, because you don't seem to understand that "casual" and "3rd coil" don't really belong in the same sentence. Anyone making any sort of headway into 3rd coil (and not just buying/leeching a win or whatever) is no casual player in my book.

For me personally, nothing about this quest feels particularly bad, whereas even 2nd coil is scary as shit for me, let alone 3rd. Yes, it's a lot of work. But not one aspect of it thus far has been particularly difficult, which is what makes it casual-friendly.