Here is the official doctrine from JW.org... (edited for brevity)
My ony interest in this thread is in addressing this theodicy as it relates to natural evil.
The real ruler of this world is Satan the Devil... That is one reason why there is so much suffering.
A second reason why there is so much suffering is that... mankind has been imperfect and sinful ever since the rebellion in the garden of Eden. Sinful humans tend to struggle for dominance, and this results in wars, oppression, and suffering.
A third reason for suffering is “time and unforeseen occurrence.” In a world without Jehovah as a protective Ruler, people may suffer because they happen to be in the wrong place at the wrong time.
Satan questioned Jehovah’s right to rule. By calling God a liar who withholds good from his subjects, Satan charged that Jehovah is a bad ruler... Satan implied that mankind would be better off without God’s rulership. This was an attack on Jehovah’s sovereignty, his right to rule... getting rid of the rebels in Eden would not have answered the question that had been raised regarding Jehovah’s right to rule.
(Illustration of a teacher and a smart arse pupil who thinks he knows better)
Millions of angels were watching.... How Jehovah handled the rebellion would greatly affect all those angels and eventually all intelligent creation. So, what has Jehovah done? He has allowed Satan to show how he would rule mankind. God has also allowed humans to govern themselves under Satan’s guidance... Jehovah knows that all honesthearted humans and angels will benefit from seeing that Satan and his fellow rebels have failed and that humans cannot govern themselves.
Why, though, has Jehovah allowed suffering to go on for so long? And why does he not prevent bad things from happening? ... In the thousands of years of human history, mankind has been able to try every form of self-rule, or human government. Mankind has made some advances in science and other fields, but injustice, poverty, crime, and war have grown ever worse. Human rule has now been shown to be a failure... Second, Jehovah has not helped Satan to rule this world. If God were to prevent horrible crimes, for instance, would he not, in effect, be supporting the case of the rebels? Would God not be making people think that perhaps humans can govern themselves without disastrous results? If Jehovah were to act in that way, he would become party to a lie.
..the ruining of our planet will be undone by the turning of the earth into Paradise. The effects of sin will be removed through faith in Jesus’ ransom sacrifice, and the effects of death will be reversed by means of the resurrection