The question is so incorrectly asked that there's no way to answer it.
The game has lots of different PvE activities and different classes do differently in those.
If you would boldly compare a raid of different classes attacking Dummy for 10 min, then most likely Scout or Paladin would win the challenge, but that would be one of the most stupid challenges to throw.
Then there's astral, which is so fast and easy that the best DPS will be the player who has his ultimates ready for the boss. Given scout's ultimates have lowest cooldowns and engi's ultimates can work together most often it's gonna be scout and most convenient difference will be from engi. But given how easy astral is nowadays and that CD on astrolaby in s16 is 10 min it doesn't really matter who's the best DPS there, coz if all group does good they will have to wait for CD anyway.
The most challenging content in the game at the moment are raids in Hard mode. The best DPS there is made by those who don't die

Other than that the differences are minor to prefer let's say scout to bard, because although bard's DPS could be lower, bard still has mass-puri and very useful ultimates that help the raid much more than a tiny bit of scout's advantage in DPS. So in HM raid it's not the DPS that matters, but what else a class is capable of.
Then there's another PvE challenge in the game: Trial of Blood. That measures the power of burst DPS mostly, but at least it can answer your question rather objectively: the class that scores more than the others is doing more damage than others.
And next week ppl will unlock Fabled Astral, which is gonna be very challenging and what would matter there is not only and not really the max DPS output, but extra features of the class that would help to actually complete an allod. That class most likely is summoner because of save abilities, off-heals and puri.