Seeing as how A3Q1 got nerfed, the ball doesn't kill all the mobs anymore
I did this with three people, A B and C.
C = most xp.
2 Players make a game and they both kill Zoltan Kulle, let's say A and B kill ZK.
C comes into the game, ports to A/B waits for A and B to leave the game.
A and B get on alternate heroes, (that did not just kill ZK) and join C.
One of the three pick up up the soulstone and get that credit ready for the quest to turn in.
A and B leave the game with their alts and resume game.
C now turns in the first quest, C joins A alt hero turns it in, A's alt and C join B's alt's game, and now all three of them turn it in.
Now resume the usual ZK cycle as usual with the mains.
A's main resumes game grabs soulstone, C and B's alt join, A with his main hero leaves the game, C and B's alt turn it in.
A's main resumes the game once again C and B's alt join, all three turn in the quest.
B now gets back on his main and resumes his game, C and A's main or alt join, B's main leaves.
C and A's hero now turn in the quest.
B's main resumes the game, A and C join the game, all three turn of them turn in the quest.
The wording might be difficult i tried, my best to word it as easy as possible. Let me know if you require more clarification. This way the runner gets some benefits instead of just standing idle in game.