Guild Wars 2

I heard from someone if any of your party members has completed story mode of a dungeon but everyone else hasn’t you can still do exp
Is that true or not

True, only 1 person needs story completed in order to open the explorable instance. He/she needs to go first to open it.

You can run an explorable mode dungeon even if you haven’t completed the dungeon’s story mode as long as one person in your group has completed the dungeon’s story mode so that they can start the dungeon in explorable mode.