Isn't every blockchain vulnerable to a similar attack? For instance in bitcoin when you get a block you could delay releasing it until immediately after you see the next winner. Some people who are closer to you on the network than to the next winner will then be forked. If you had enough mining power and fast connections to different places in the world, you might be able to fork off a significant amount of hash power this way.
Yes. A long block interval softens the issue a bit because there is more time for information to propagate.
As you reduce block interval times connectivity gets more weight. Move block intervals to very very small values and effectively your connectivity will determine the winning chain (given a reasonable distribution of forgers/miners).