My guild has been delighted with the style and difficulty of GW2 dungeons, particularly Explorable mode. It seems that many people are having great difficulty getting through Story mode however and I thought I could offer some tips to help un-WoW yourself (this isn't a slight - I am proud of my prepatch Firelord title)
Defense is more important than offense, especially if you ever want to melee
This is the biggest mistake I see happening. Dual dagger thieves building glass cannon. Axe warriors in all power/precision gear. In general, the more offensive traits you take to make your build work, the more you need to compensate on your gear with defensive stats. Melee weapons in particular do much more damage than their ranged counter parts thus you can afford to stack more defensive abilities to allow you to get in there and take a hit.
Condition and boon management are something the group has to figure out together.
Protection increases your effective HP by 50%. Blindness is heavily penalized against bosses with Defiance but wildly useful otherwise. No matter how well you dodge, a 20 second boss poison will kill you. You need to look at your abilities (and your group mates) and at the very least have a solution for enemy conditions and regeneration/protection uptime. I realize the game is very new and there is a ton of depth to skill and trait configuration, but try to keep in mind that if you go into a dungeon with 5 DPS-focused leveling builds, you will die constantly.
CC is, as usual, king
Chilled, Crippled, Stun, Daze and more unconventionally Reflections/Absorptions are all necessary to complete dungeons without constant deaths because...
Ranged enemies are always priority targets
Ranged enemies are brutal vicious thugs in this game when you allow them to turret and waste your party. Enemy melee are very kiteable which is why it is important that they are kited until ranged threats are eliminated. All those Reflections/Absorptions that you glossed over when leveling because you thought they were useless? Try them again now. It's amazing how quick you can burn down a ranged enemy while inside bubbles of protective love.
Interrupts work through defiance
You won't get the stun or the daze effect, but unless you actually see "Immune" pop over their head when you use these effects, they will still interrupt skills.
Reviving downed players should always be your number one priority
This seems obvious but is the biggest failure of PUGs in particular. One alive team member can help a downed played get up in seconds. This is crucial to gameflow, even when death usually means a sprint back from the waypoint. The reason everyone feels like they're death zerging is because they sit and watch their downed team mates die while trying to beat the non existent damage meter. Quick revives are basically the GW2 version of healing in the traditional MMO sense and now everyone is responsible for it. Look again at your trait lines, specifically the vitality line - all those "on revive" traits start to look very good when you realize how often to need to be doing this.
You will only get good at dodging when you stop staring at your ability bar to hit DPS buttons on cooldown and start paying attention to the fight itself.
This comes with practice, but again, non existent DPS meter versus winning the fight. You decide.
Things I think are currently brokenish
•Trash is usually way harder than boss fights. Something needs to give.
•There needs to be a huge pinging "I AM DOWN" type button, it can be very difficult to actually locate downed team mates in the chaos
•I generally think there needs to be a range buff for nearly all effects that work on allies. The game wants you to spread out a lot to avoid AoE and then penalizes you by making all your group buffs relatively short range. This could easily be PVE-only.
•I still think getting into melee might be too punishing even with full defensive gear.
•The best bosses are the ones with tells that can be easily seen through all the spell effects. They're always there, mind you, just perhaps need a little emphasis.
So that's that. Feel free to add your own success stories and strategies, especially for specific dungeons and their encounters.