S= Soulstone quest
T= Tyrael Quest

Phase 1:

Player A (3xS/5xT)
1- Once you recieve an invite, Join and wait for update, banner to me once belial is dead.
2- Leave and resume your game, wait for player B and C to show up
3- Turn in both quest (1xS/1xT)
4- Leave and join my game

Player B (4xS/7xT)
1- Once you recieve an invite, Join and wait for update, banner to me once belial is dead.
2- Leave and resume your game, wait for player C
3- Turn in both quest (1xS/1xT)
4- Join Player A's Game wait for Player C and Turn in both quest (2xS/2xT)
5- Leave and join my game

Player C (5xS/9xT)
1- Once you recieve an invite, Join and wait for update, banner to me once belial is dead.
2- Leave resume your game and Turn in both quest (1xS/1xT)
3- Join Player B's game, Turn in both quest (2xS/2xT)
4- Join Player A's Game, wait for player B, Turn in both quest (3xS/3xT)
5- Leave and join my game

Phase 2:

1 of the player Banners to me and wait for me to leave
Player A,B and C will take both quests.
They will then all join my resumed game where i will take the soulstone quest, (DO NOT TALK TO TYRAEL JUST YET)
- Bringing Player A to 3xS/2xT
- Bringing Player B to 4xS/3xT
- Bringing Player C to 5xS/4xT

Phase 3:

Player A
1- Leave the game and resume yours, Wait for player B and C.
2- Once they are all in the game, take the quest (3xS/3xT)
3- Join my game, wait for player B and C to join and me to leave
4- Turn in the quest to Tyrael (3xS/4xT)
5- Leave and join my resumed game, wait for player B and C
6- Turn in the quest to tyrael (3xS/5xT) and the run is over

Player B
1- Leave the game and resume yours, wait for player C
2- Once he's in the game turn in the quest (4xS/4xT)
3- Join Player A's Resumed game, wait for player C then turn in the quest (4xS/5xT)
4- Join my game, wait for me to leave and player A and C to join, then turn in the quest (4xS/6xT)
5- Join my resumed game wait for player A and C to join, turn in the last quest (4xS/7xT) and the run is over.

Player C
1- Leave the game, resume yours and turn in the quest (5xS/5xT)
2- Join Player B's resumed game and turn in the quest (5xS/6xT)
3- Join player A's Resumed game, wait for player B, then turn in the quest ( 5xS/7xT)
4- Join my game, wait for me to leave and player A, B to join, turn in the quest (5xS/8xT)
5- Join my resumed game, wait for Player A, and B to join, we turn in the final quest and the run is done (5xS/9xT)

some ppl do both quests at the same time but that limits the exp imo.