If you're just doing leveling, I would suggest Dolmens. Dungeons might be worth it, but not so sure about that, unless you got one with a huge spawn that happens nonstop. What I have found is that I have a lot more fun if I do world quests because you get to experience much more of the story and the adventure. I used to just do the Dolmens, but now I do the story and explore new areas.
Here is the thing, if you power level to 50 with a Grind, your going to have 64 Skill Points when you get there. Pretty useless as a character really. So, you have to chase Skyshards in order to fill out your skills and more important your passives. So, just chase the skyshards, you have to anyway, and you save time in the long run.
Let me give you an example of what I did with my last two leveling characters.
1. I collected all the Skyshards in the zone. I avoided any and all quests other than those that show up in the delves that have skyshards. These quests do not give set items for rewards so no loss there.
2. I would farm the dolmens a few times to get set jewelry that helped my character
3. I would do the Public Dungeons including all the bosses
4. Then I would move to the next zone.
In doing this, I could fully gear up my character with level appropriate stuff, and it was helpful gear. May not have been the best, but you don't need the best while leveling. Any gear I farmed from Dolmens or PD's is repeatable, so I can get it at CP160 by just repeating. Then, I had all the content quests left for me once I reached CP160 as those can give you sweet Set Drops in good traits you want. And, Quest Experience is huge for gaining CPs once your past CP160. Kind of a waste before that.
In about 8 zones, I would be fully leveled in Mages, Fighters, Class, 3 Armors and Weapon Skills. Leaving only Undaunted to level, although I would get to almost 3 in that from Dungeon Achievements.
Enjoy the game, life is what you really want to be worried about.
PakKat "Everything was going well, until I died"
Gary Gravestink "I am glad you died, I needed the help"
I agree with Nestor for getting to level 50. I'd maybe point to the skill points you get from each version of every dungeon too, but still wait to do them. Dungeons themselves award very pathetic experience overall, at least as far as progression goes. However, dungeon achievements are the fast track to getting Undaunted passives, but you won't unlock Undaunted until level 45. So while the progression through dungeons is very slow, doing them is still ultimately worthwhile. It's worth noting that it can also be rather disappointing to get a gear drop from dungeons that you'd like to use, but it's at level (insert random <50) so it's worthless in the long run.
Follow what Nestor says, then once you hit 50, find a decent group of people to just go through all of the dungeons together, starting with Normal difficulty. Then on vet dungeons, focus on getting the Slayer achievements primarily (which almost all take more than a single run). If you've got a good group, go for the No-Death and Speed challenges too. Sweeping the dungeons like this once you hit level 50 will not only progress your character, but will serve as a decent stepping stone into more difficult content too, easing you bit by bit through tougher stuff.