These bummed me out at the time:
artist, year died, age:
Otis Redding, 1967, 26
Jimi Hendrix, 1970, 27
Janis Joplin, 1970, 27
Jim Morrison, 1971, 27
Duane Allman, 1971, 24
Berry Oakley, 1972, 24
Elvis Presley, 1977, 42
John Lennon, 1980, 40
John Belushi, 1982, 33
Buddy Rich, 1987, 69
Jaco Pastorius, 1987, 35
Miles Davis, 1991, 65
Jerry Garcia, 1995, 53
John Denver, 1997, 53
George Harrison, 2001, 58
Ray Charles, 2004, 73
Dan Fogelberg, 2007, 56
Joe Cocker, 2014, 70
Glenn Frey, 2016, 67
There were many others which saddened me upon hearing. Overall, the younger they went, the higher the shock. Despite that, most shocking to me was John Lennon due to the unfortunate circumstances of his death. I left off some who were older when they died, and had long, successful careers, and saddened me in a "legend dies" way, but wasn't so unexpected due to age and health (eg, B B King, Johnny Cash, & others).