The positioning of the Corrupted Soul fragments can be controlled by having players with the debuff run to specific locations (e.g. world raid markers). This will allow your DPS to cleave the fragments down evenly until they are low on health, so the fragments can be easily and quickly killed when the players inside the stomach are ready to exit.
After a player successfully exits Gorefiend's stomach, their Gorefiend's Corruption debuff will have a 15-minute duration. If a player dies - either through accident or by being targeted again with Shadow of Death - while affected by this debuff, they are not transported to Gorefiend's stomach, but are simply killed.
Gorefiend's Corruption can only be removed by colliding with an Unstable Soul during the Feast of Souls phase. Players afflicted by Gorefiend's Corruption must be sure to clear this debuff so that they are not outright killed by Shadow of Death. It is not viable to have a tank, or a player with strong survivability cooldowns, collapse all of the Unstable Souls during the Feast of Souls phase.
As shown in the table above, tanks will be sent into Gorefiend's stomach twice per phase instead of only once. This means the raid must kill two Gorebound Spirits, and must kill the first Gorebound Spirit before the second tank is sent into the stomach. This gives the raid around 30 seconds to kill the first Gorebound Spirit. It remains the highest-priority add target.
Finally, in Mythic difficulty, Shared Fate will affect a total of 4 players each time, instead of 3. This poses no additional strategy constraints, but requires the raid to be more vigilant than on Normal/Heroic difficulty.