Replaying story mode
You can choose if you want to enter story mode or explorable when you approach the dungeon.
You can bring someone into explorable if you have completed story mode yourself or anyone in the party if they have completed story mode can load an explorable version of the dungeon for the rest of the party.
You should have full compliment of 5 people for the Ascalon Catacombs.
Excellent thanks very much