I was paying attention; I didn't say that you needed to defend against all attacks at once. But for you to be ready for whatever our next attack is, unless Dwarves can see the future, you would have to be prepared for any assault, no matter what it is. The cement sphere is the only thing I can think of that would protect you from all of our possible assaults. If you can think of a better defense mechanism, go for it. Unless, of course, Gandalf or someone will be supplying you with magic that will adapt to fend off whatever we throw at you; but you didn't mention any wizards.
And if the Dwarves are outside of their cement ball, they can't very well defend against our next attack, whatever it is, can they?
*baby Elf spits up all over the tent thieves*