GW2 doesn't really have a trifecta like other MMOs, so there aren't strict tank, healer or DPS roles. In fact, the most efficient (I'm talking speed) way of clearing dungeons is 5 high DPS characters. I mentioned before that I haven't reaaally played for a couple of months, so maybe that's changed by now, but I doubt it.
No, it still holds true for the most part.
Vanilla areas are largely untouched as that any Build works.
Some clear it faster, some survive more easily etc.
However, Heart of Thorns did add several new maps to the game.
And on these Map's specifically things changed quite a bit.
In the first little while it was almost unplayable with a DPS, enemies focused too much on going right at you and doing heavy damage.
However, after a bit it seemed to get tweaked a little so DPS is still playable in such areas. But admittedly it is harder than it is for a Tanky build.
So in a nutshell.
Vanilla Maps = Good for everyone, DPS simply adds a little more risk for faster potential.
Expansion Maps = Slanted in Favor of Tanky Builds. DPS can make it but not as well.
It is a design choice I personally have some issues with, because it's started this mentality that I can only describe as "Tank Build Master Race" where people are starting to view DPS builds as inferior and outdated. Which spits right in the face of one of Guild Wars 2's main attractions, play how you want.
But at the same time, I can see why they did that.
The reason I picked DPS for my current Main is because the point of my main is to gather gold, resources etc to support future characters.
And one can gain resources the fastest as a DPS, so they do have a built in advantage over that.
So at the same time, it's fair to have Tanks get an advantage somewhere as well.
But yea, just note that with the expansion different maps treat builds differently.