Firstly, this is the Localization forum - for discussing grammar and spelling errors and the translation from Japanese to English. For issues like this, you can try the dungeon forum at https://forum.square-enix.com/ffxiv/forums/648

I did the dungeons as a Viper (a DPS). I got some vuln stacks but I got through them. I'd likely be able to get lots of vuln stacks as a tank, so I'd suggest trying the dungeons as a tank - particularly Paladin or Warrior which have an abundance of self-heals.

If you struggle with Duty Support, you could try recruiting in Party Finder for 3 people to help you clear the dungeon and explain that you struggle with it.

8 deaths is actually pretty common in the video games I grew up with - a lot more, in fact. This game is generous in allowing you to beat story content in 1 or 2 tries in many cases, but they had complaints about it being too slow and boring for some players, so they tried to make it "more exciting". It's not necessarily harder in that you can survive with vuln stacks so that repeated mistakes are what can get you. Normally you'd get resurrected if you die, because normally other players would just complete the fight even if you're dying a lot, but with Duty Support it resets the fight the moment you die.

I do agree with you that all games should have an "easy mode" and a "hard mode" and I do wish this was the case for all content, including dungeons. But for whatever reason, it's not and there are ways you can improve it as I suggested - being a tank, using Moqueca (food) for the extra HP and doing it with other players.