Just want to clarify that I agree entirely with your ruling here, and that was what I was trying to convey. Apologies if I didn't make that clear :blush:. Fireball can't go through it, becuase it requires a streak to physically pass through the WoF. I was just contrasting to a physical, opaque...
I disagree, as a normal wall would conceal the target and a wall of force does not. The gist of the cover rules on 196 of the PHB seem to deal more with difficulties seeing and therefore targetting creatures, rather than any physical impediment to striking them whilst they're in direct view of...