I’ll tempt fate and comment here.
GW2 took a different path on Dungeons entirely. An abandonment of many of the concepts you vaguely highlighted, in favor of embracing new sorts of challenges. But, why not hit your points one by one?
High Difficulty:
This one is a trick. MOST dungeon routes are generally do-able with most party compositions. That is, the trick is you have to learn what element is troublesome, and then find the way around it. Party formations, when to dodge, who to take out first, or a more complicated objective. These are some of those elements that the players have to adapt to. It’s sort of the mentality of Demons Souls, really. The game makes you adapt to it until you are good enough to handle the challenge.
Rewards and XP too low:
I might beg to differ on this one. While learning a dungeon may have a higher armor repair cost, it generally, on a very bad run, will neutralize the rewards you get for completion, this not including the value of dropped items. XP is another case entirely, with almost a level gained per dungeon run at level 80.
Traps:
This is an element of caution. A wary party would be wise to probe for what lays ahead than jumping into the fray unprepared. Entirely an element of the experience of the dungeon.
Additional mobs/agro:
For the most part, this isn’t too much of an issue. Some dungeon sequences will send a large number of foes fairly quickly, but quick adaptation can handle this in many cases. For the majority of the dungeon, a party can siphon off a bite sized chunk of mob that they can handle.
Group Search:
Location and Organization here.
A. Form up outside the dungeon for pick up groups.
B. Wait in a major city (Lion’s Arch) to recruit or find other groups
C. Form/Join a guild and run with them.
It may be nice to have a specific feature, but options are there.
Healing/Tank (Trinity)
Individually, and as a group, players are ultimately responsible for their own survivability. Ranged can stay alive fairly easily by keeping out of range of foes that will deal heavy damage to them. Melee can use well timed dodge maneuvers, and if worse comes to worse, have the party fall in to keep alive. There’s no need for a tank/damage/heal setup here. The responsibility is on the individual player to keep themselves alive, and if that fails, to keep each other up and moving. It’s a coordinated effort, but by no means is there a need for the trinity. Each player can fulfill those functions on their own. What teamwork means here is every player working together to accomplish that same objective—taking out the hardest foe first so it doesn’t overwhelm the party, not that the healer keeps the tank alive and the damage dealer to just unleash damage nonstop. It’s a more dynamic experience, more involved, and that level of individual responsibility greatly stimulates group work to achieve the greater objectives.
No reason to do Dungeons:
Comradery? Tokens? Armor? The thrill of experiencing the more developed, and puzzling aspects of the game? Drops and money aren’t the only reasons for Dungeons.
Level Limit Breaks dungeons:
This is a fun point to note. See, the level cap per dungeon actually makes balancing particularly easy. A team of players will have a relatively consistent challenge, regardless of their actual level. There’s no level 80 requirement for Ascalon Catacombs, and a level 80 will have a similar challenge to that of a level 35. That being said, the rewards can also be balanced for a level 80 just as they can for a level 35. The level cap genuinely makes dungeons better. The experience will remain the same, even if your level doesn’t.
GW2 aspired to follow it’s own path. What you are suggesting is that the game adopts some of the elements it chose to break away from, and hinder the experience they intended to create.
But, I ramble here.
