Clairvoyance makes Obscure a moot point, though eventually, even with, that Obscure would be useful if we use it to do teleporting strikes.
I figure we could approach that type of spell two ways either we actually teleport anyway in Darkness/shadow (using Obscure this means anywhere in our range) and then attack or we meld into the Darkness and essentially make thousands of attacks per second due to the fact that we can move our strike mid-attack to a new location.
Or if you want to get more broken, move at the speed of Darkness, which is essentially equal to or greater than the speed of light.
So physical base vs. conceptual base for the spell. The latter would be higher end likely just due to the fact that it is conceptual, but still.
And wow, I went way off my original topic.