When we say "How is god just, when all these tragedies are occurring in the world?", we assume that god is thinking like us. In our view a person committing genocide is deserving of a severe punishment, but god isn't a person. He is the most just, and the most knowledgable(not sure about this view in every religion, but it is viewed as a truth in Islam). According to god, we as humans have a limited view of things, we can't see the big picture. We don't know where the world will be in 100 years, but god knows how it will end. So in my opinion, we can't ask god to justify his actions, because he doesn't think like us, he knows better than us. Now I'm not saying you can't question a religion, questions are important, but we shouldn't bash on each others religions and cause conflict. Who knows what's right.
A man argues for or against a deity and that deity must be called into account for various behaviors, actions, and general attitudes as well as it's nature in order to be debated upon. If one presumes that a deity thinks far beyond the level of man in an incomprehensible manner then one cannot actually produce any form of argumentation let alone even scarcely approach the subject.