They'll fix it when enough paying players decide the fix is worth cutting off their money until said fix happens. DE will never change their MO while the dollars continue to come in.
They could make a fix by caching rewards on all squad member's devices, using the host's as the default as they already do, and relying on whoever becomes the host if the first disconnects. Considering that even for longer runs the data shouldn't be insane I'm not sure why they can't implement that if they choose not to write it to the server. They could even write the mission state to at least some level of
