Maybe I’ll sound like some sort of apologist for the game, but I can’t recall having either of those things happen to me more than once in leveling one character to 80… though to be honest I did level Artificing to near 400 and I did a bit of WvW, so I may have gained 15 to 18 levels from that, so it’s only 60+ levels in the field.
But in all my adventures I can’t recall issues completing hearts. Busted dynamic quests, sure, I’ve seen those. And broken skill points, sure. But not what you describe.
I agree that AC is a pretty tough instance to start people on, and that CM (and Twilight Manor, which is the level 50 dungeon) are much easier. I honestly don’t understand why they made the first dungeon so brutally difficult.
I’m not sure you need all the tools you list above - I’ve never felt compelled to have cooking consumables or artificer potions, but I do understand combos, and I keep my gear pretty up to date. Having people who understand their class and how it interacts with other classes does make AC much easier. I have done story mode maybe three times and the last time I did it, with a bunch of Wanderers, it was smooth as silk, and even those nasty 3 pulls of Monk + Elementalist + Warrior weren’s too terrilbly bad - I don’t know if it’s the group makeup, or what, but we just clicked.
One aspect that makes things easier is if people spec a bit more defensively. As a Mesmer, I always have Feedback and Null Field equipped, but I swapped out my standard Radiation Field for the Phantasmal Disenchanter, who removes conditions.
One thing that really helps is to call targets - ctrl - T on a mob and everyone will get a callout to target them by hitting T. Plus they get a big red targeting icon above their heads. This helps ensure everyone is attacking the same mob.
Another thing is to realize that people will get downed, and you’ve just got to get them back up (or let them run back from the waypoint, since there’s no real penalty to doing so, outside of the downed debuf).
People will get more aware of their class and abilities over time, all I can say I guess is hang in there!