The best way to defend against lumberjack and balloons is to take minions in your deck or target the balloon first and then the lumberjack. Even if you have a defensive builder that will not work because the opponent deploys the lumberjack first, it's better to make minions with you in a deck. To counter against lumberjack and balloons decks, you can also take bats, mega minions, electro wizards, or freeze.