How much structure should we put into our shared responsibilities? Should all tasks be grouped, alloted, and tracked before hand?
This depends on the situation and the nature of the responsibilities - when we're in a very dynamic situation like a fire-fighting on-call rotation - it's not possible to foresee all situations before hand. While there are always things that can be discussed - things are changing and so dynamic that the tasks may not fit into the neat time allotments that we gave them. In such situations we must at least be mindful of slippage and be ready to take remedial action (alert someone else, for example).
In a less formal setting like family responsibilities - the added expectations and emotional responses make this a bit more difficult - the importance, priority, and deadline of tasks are amorphous and change with the people, time and mood. In such situations - it's better for everyone to simply expect and *allow* slippage from others - knowing that it's not avoidable. Today, it might be you forgiving someone not being up to the task - tomorrow you might be the one let go easy.
Sharing responsibilities is a 60-40 burden, where both parties are trying to be on the 60 side.