Visibility and discussion.
So regarding this, resolution of attacks includes allocation of wounds? I agree that you resolve all attacks against one unit before moving to the next, but the rules state that you don't allocate wounds until after all of a unit's attacks have been resolved.
The core rules for "Allocating wounds" state: "Once all of a unit’s attacks have been resolved, add up the damage that was inflicted," followed by, "wounds are allocated one at a time to models in the target unit. You can allocate the wounds inflicted on your units as you see fit (the models do not have to be within range or visible to the attacking unit). However, if you allocate a wound to a model, you must keep on allocating wounds to that model until it is slain – a unit can never have more than one wounded model."
The reason this portion of the rules doesn't fully answer my question is that it only refers to a singular "target unit" , but in the next sentence goes on to say, "You can allocate the wounds inflicted on your units as you see fit" (emphasis mine). Taking the whole section together leads me to believe that, as long as I don't have inflicted wounds on more than 1 model in each unit at a time, I can freely switch between allocating wounds to 1 unit then another.