No one has ever died directly from an MDMA overdose (as far as I know). Yes there have been indirect deaths usually from over-hydration (which causes the brain to swell, with or without MDMA), which usually happens in a rave/dance setting.
I'm sure there have been many indirect deaths from cannabis as well. Lung cancer, car crashes, falling down an elevator shaft, etc.
This is going to be true of any sufficiently powerful psychoactive substance.