Yes, a big die off on the Great Coral Reef indicates the negative influence of global warming. Warmer air current temperatures that result from global warming cause an alteration in the chemistry of the ocean, which subsequently induces bleaching events in the coral reef. This can be shown to be the result of processes that are happening very quickly, and so are unlikely to be occurring without the influence of accelerating activity like green house gas emissions.
Yes, the record die-off of the Great Coral Reef is evidence of global warming. It is another sign that the planet is warming at alarming rates. You would think any one of the many signs would act as an alarm, but so far there seem to be a lot of people hitting the snooze button. Maybe the fact that such a great natural monument is being destroyed will make an impact.
Bleaching events, when the water surrounding a coral reef becomes too warm and forces the coral to expel the algae that grow on its surface, are increasing dramatically. It seems hard to escape the conclusion that these events are becoming more frequent because the water in the region is becoming hotter as a result of climate change.
There is a difference between weather and climate. There is a difference between global warming and evolution. In order for some species to evolve in better ways, other species have to die off. The Great Coral Reef might shrink, but that means some other pattern in the oceans will emerge. This is the circle of life.