I would would rate all of them above 5 and I would put natural evil at the top of the chart with a 9 out of 10.
You're right about this rating. The problem of natural evil is the hardest in theology.
But natural evil is a by-product of natural laws. And natural laws probably are a necessity in a world suited to free-willed agents.
Necessity truths are universal in all possible worlds and come directly from God's nature and not God's will.
IMHO natural evil is a necessity in a world of free-willed agents. But they are temporary in the lifetime of people and I believe the ultimate God's will is to achieve a greater good. Just like parents submitting their children to painful medical procedures.