Timing: Dark Elf Corsairs vs. The Final Rotting resolution order?

By Pweent, in Chaos in the Old World

Both The Final Rotting (Nurgle chaos card) and Dark Elf Corsairs (Old World card) resolve at the end of the battle phase. In what order should these be resolved? Here's what we ran up against.

Dark Elf Corsairs have an event token in Estalia. Nurgle has played The Final Rotting in Estalia, and has 5 corruption tokens there. After battles have been fought, the following figures remain:

- Tzeench's Lord of Change and four cultists

- Khorne: One cultist

- Nurgle: Two cultists and one plaguebearer demon

If Nurgle's Final Rotting is resolved first, he uses his five removals to clear out all five opposing cultists. The Dark Elf Corsairs then eliminate one Nurgle cultist, the Khorne cultist, and the Lord of Change. Only Nurgle forces are left in Estalia.

If the Corsairs resolve first, Tzeench can choose to remove one of his cultists as their target. When The Final Rotting is resolved, Nurgle has only three Tzeench cultists to target. The Final Rotting only affects cultists and warriors, so the Lord of Change remain on the board in play.

Is there a ruling here? There's no place that I can find for the Old World in the player turn order, as they usually occur in the Old World phases.

I don't know of any specific ruling - the general principle for governing anything with Old World cards is lowest threat chooses - so I'd say a reasonable option would be the lowest threat player decides whether the Old World crd is first or last.