Guild Wars 2

1st Will dungeons still reward us the same amount of XP?
2nd Will dungeon XP count for leveling masteries?
3rd Will we be able to level pact tyria masteries by doing halloween content?

If it would normally give you XP, it’s going to give you mastery XP at level 80. If it’s not a part of HoT, it’ll count towards Pact Tyria.

The experience rewarded in dungeons is based on a percentage of the experience required for your level. The amount will stay the same for a level 80, however it will continuously feel like less due to the mastery bar increasing in the amount of experience required.

1: Perhaps, but it does mean that you will have to run a dungeon several times to level a Pact Tyria Masteries, as dungeons would only count towards that. Also, Mastery XP requirements double each level.

2: Probably, and see answer 1 for what that would mean.

3: I don’t see why not. The Halloween content would be based in Tyria most likely, as it is part of the vanilla game.