Drake attacking shows through "fog of war" allowing you to see enemy fighting drake with no vision.

So. I'm not sure if this has always been this way, but I am assuming it hasn't been.

But it was either cloud or ocean drake which did that in particular, but I was hovering over where the Drake was on the map, using freecam, and I saw the particle effects it leaves when it attacks, even though we had no vision of the area, it was like flashes of light, and then the drake got slain. This means you can tell when an enemy is fighting the drake without needing to place a ward. May have been circumstantial tho.