Gotcha!
One more question if you don't mind about the 'shared enhancements' node on Ballista.
Based on how you said things with work penetration (that the node DOESN'T apply to penetration) I assume it also doesn't work with other things that increase your 'damage' overall, but aren't explicitly adding raw damage.
For example, it wouldn't work with 'Attack Speed'. Because even though attack speed technically increases your damage, it itself is not a 'damage' stat, it just augments your damage stats.
Therefore, the only 'Attack Speed' that would benefit Ballista's are minion attack speed, Ballista Attack Speed, and Attack Speed from the Ballista's tree itself.
Is how I'm conceptualizing that correct?