Great idea for defending against spells

Well, as we all know new spells have been added in the last update.
I think its a little bit OP, so i begin to search for a solution.

A new defencive building, called spell shield
Its a 2x2 building and can be unlocked at TH8 (because you can unlock dark spells at th8)
It will make a shield around the buildings inside of the circle, i thought the range would be 6 tiles and 7 tiles at lvl 2.
The building cost is 2million gold
The second upgrade costs 5million and can be unlocked at TH9 (maybe TH10, im not sure)

Well this is how it works and its weaknesses, this shield can absorbs any spell but is weak against one spell, the lightning spell. When you drop a lightning spell on it, it will shut down the shield for some 30 seconds (20 at lvl2)
But when the shield is active and you drop a spell on it, its gone.
When u drop it on the sides, the spell will not get into the circle, but will still works next to it (so you got something like a half moon spell).

I hope you like the idea, if i forgot anything tell me and ill add.