That bolded part is the attitude you should keep! ;D
Just because something doesnt work out the first time doesnt mean its to difficult or that you should hold a grudge or get upset about - thats how stuff is sometimes in life and videogames. Maybe you had a bad party. Or maybe you hadnt figured out a good way to use your own skills yet. Or maybe something took you by surprise.
I remember (painfully...) how many tries it took me to beat Efrye in FFX... okay, no, I actually dont remember how many, because its one blury, painful afternoon from 10 years ago.
Just yesterday I was playing a game called Epistory and some fights took me 2 or 3 times to beat - but thats okay! At least I'm not bored by it!
Sometimes things will go wrong and the question you should ask yourself isnt "Is this content to difficult?" but "Mmh, what went wrong here and how can we fix this?" - maybe its your group, maybe its you, maybe its both.
But shying away from anything that even remotely looks like it could end up being a tiny challenge is what will make this game boring and bland for everyone in the long run.
Dont give up at the first little bumper and "cry for nerfs" (even though I do acknowledge that thats not excatly what you did, but honestly: close enough).
Not everything has or will go smooth during the first try - not even in casual content. And that has nothing to do with "savage diffculty" (man, I wish, that it would be only one wipe in savage... instead of two hours of wiping to a boss the whole group actually cleared already... I disgress) - it has something to do with you actually being required to know your toolkit, know basic mechanics and execute them - all fairly reasonable for someone who reached the max level of a game.