What content has gated you, and for how long?
I had trouble with Titan HM. I couldn't memorize all the mechanics. To my great embarrassment, I got through shattering the heart and then died and was carried the rest of the way. I have yet to try any of the new dungeons besides CT.

Why are you stuck here?
My memory isn't great. I have probs with 'tunnel vision' too I guess. Running out of aoe doesn't mean anything.
Mostly though, I am terrified of embarrassing myself in front of others and being called 'bad'.

Are you upset about this? (if so - why? and how can content be added for more hardcore players such as myself without upsetting you.)
Not upset really. I'll get there some day. I just hope others will be willing to go with me when I do. It is not unusual to put out a call for a particular dungeon and just hear crickets chirping.

Should any changes be made to the content to accomodate you and players like yourself?

Changes to content? Nah.
It'd be neat to have more mid-level dungeons though.
It would be a big help to have lag/latency dealt with.
It would be nice to not have queue times of an hour.
It doesn't help that it seems the "ideal" strategy for a dungeon or fight changes every couple days.

Most of this is just "I need to practice more". I won't go without friends though.

Full disclosure - this is my first regular mmo.

btw, I like these kind of discussions. We get to see what motivates other players.