It happens everytime, if you or any teammate is dead when someone else from your team kills the dragon, the dead teammate will not receive the 4 elemental stacks, neither the elder dragon buff.
The elder dragon buff makes sense (even if you don't lose it when you die), but not receiving the 4 stacks just because you're dead is very annoying because the elemental buffs make a HUGE difference.
1. gather your team to kill the dragon
2. KILL YOURSELF
3. let them kill the dragon while you're dead
4. get mad because you didn't get the stacks/buffs