Again read what i said.
The OP did not complain once
Forum complains about other people complaining based on their own assumption that everyone is complaining, so typical... The OP said his party is well balanced and well experienced, I am pretty sure he tried 10-15+ times with different strategies and is having no luck and therefore is asking at the forums.
My guess? All 35+ content is unbalanced as it has had zero public testing XD
Sorry, I saw the Thread Title and all I could think was the level 15 quest fiasco all over again. I haven't done instances that high yet. Are you all geared up with new gear and not the old 1.0 gear? Could there be a mechanic you might be missing (the bomb/slime fight in one of the other dungeons) you might just need better gear is the one thing that comes to my mind. Get it all melded up and such, but I'm pretty sure you have already thought of all of this. I doubt they would make something intentionally impossible to beat. I'm sure there is a way. Just think of the thrill of accomplishment you will get when you finally figure it out. That seems to be what people are saying is missing from this game. (other's words, not mine.)
Just keep running it like BeyondTheLimitation when they fought Pandemonium Warden in FFXI XD. Run it till you passed out or start getting sick.
I learn absoluty nothing because i breeze everything.... so far the game is insulting in term of difficulty....
We know that was going to happen nobody will be gear prepare for high lvl stuff so we will have to upgrade crafting during freaking all day long to be able to do better gear to go end game... BAD GAME DESIGN !!
Right here, you take little to no effort to learn about your target and simply zerg through the dungeon and then do the same thing at a higher level and expect the same results. It's your fault, not the games.. the early levels teach you the basics of what to expect, yet you choose to ignore these. Then there are other people who are careless simply because "It's easy, we wont die anyway" where a CNJ would run far ahead of the tank or a THM not watching his hate meter, DDs not paying attention to ads or tanks not rounding up the monsters properly.
If you power leveled to 50 you likely have really crappy gear. This could be a reason why you cannot complete these dungeons. I've seen 50's on Leviathan that I have better gear then at 40.