1. Difficult to search out Nagato and have another in hand without being tempo'd to death.
2. Like everyone is saying, isn't nagation a good enough answer? Hina, Dehydration, even Ino. Isn't that hard to counter people.
3. Who is actually losing by turn 7? Granted, void can turn marker pump. But the entire void deck needs to be revolved around it. Otherwise he's just a turn 6 or 7.
If you guys are losing to it, you simply just don't have a good enough side deck. Your going against void people. One of the worst draw powered decks, the only element where you have to sacrifice while deploying, and currently has 1 or 2 offensive jutsus and that's it. It is a funny combo. Great even. But difficult to pull off with such a bad mono deck.