Blizzard has released data about the first hours of Classic Hardcore. In a little over 24 hours since launch, 90,000 characters have perished. The highest-level player after one day reached level 33!
In these first 24 hours, the deadliest mobs in Classic Hardcore were:
Blizzard also compiled in their post a heatmap showing deaths every 2 hours:
Heatmap at the end of the gif: