Under no circumstances does HW MSQ require ARR EX or Coil-level expertise. Most players progress through HW (and this entire game) without ever touching the old EX primals synced, much less Coil—which is a very old raid that you will have a very hard time finding a group for that will want to do the raid properly (it’s standard now to just unsync it with Echo so that players can experience the story, as it was a very story-heavy raid that tied into the final events of 1.0). That said, Coil itself has undergone several nerfs, and is nothing like what it used to be. It would still be challenging, but not as challenging as it was back in the day. But again—you don’t need to clear Ifrit EX or Final Coil synced to do any of the MSQ in this game.
I would think that your struggles lie in your gear being inadequate for the content you are tackling coupled with still learning your job. Though MSQ content is easy, gear is still important. Assuming that previous posters were correct in you wearing i90 on your left side, you are 25 item levels below the minimum item level that HW started out with. I see on your Lodestone that you now how some i115 pieces, so that should hopefully alleviate some of your issues with taking too much damage.
If you’re that concerned with gaining more skill, just practice your job in any setting. It doesn’t have to be EX or Savage. Look at your tooltips, maybe look around for some advice/tips/guides on how to play SCH better, and go from there. Throwing yourself into old high-end content isn’t necessary to get better at the game.
