I've noticed in my last two playthroughs of the game that I only get legendary quick hacks once I reach level 34 or so. Early levels I start out only getting green quick hacks, and after a few levels I start getting blue quick hacks. I usually don't get epic quick hacks until my character's level reaches late teens/early twenties.
I typically do not rush to the higher level areas for legendary quicks. Instead, I sort of play the zones in their recommended order (Watson > Westbrook > Pacifica > Santo Domingo > Badlands > Heywood > City Center), and I've noticed that I only start getting legendary quick hacks when I'm in the mid-thirties and exploring Santa Domingo or higher. I have received legendary quick hacks in lower level areas like Watson, but only when my character's level was in the thirties.
I typically do not rush to the higher level areas for legendary quicks. Instead, I sort of play the zones in their recommended order (Watson > Westbrook > Pacifica > Santo Domingo > Badlands > Heywood > City Center), and I've noticed that I only start getting legendary quick hacks when I'm in the mid-thirties and exploring Santa Domingo or higher. I have received legendary quick hacks in lower level areas like Watson, but only when my character's level was in the thirties.