How many times have you been in a Raid or Nightfall type game?

That's the key, right there. Legendary engrams do drop during patrol and story missions, but they're extremely rare. If you play Nightfalls, vanguard ROC and Dragon strikes, weekly and daily heroics, you'll see a steady stream of legendary engrams. Plus you'll be ranking-up your vanguard and Cryptarch level, which grants you legendary engrams some of the time.

Raids don't drop legendary engrams, but they do yield legendary raid items: armor, weapons, ships, and class items.

Raids also(for some reason) help increase Legendary Engrams out in the wild. Every time I finish a Raid, within 15 minutes of starting Patrol, one just drops right onto the floor. It's amazing!

How many times have you been in a Raid or Nightfall type game?

That's the key, right there. Legendary engrams do drop during patrol and story missions, but they're extremely rare. If you play Nightfalls, vanguard ROC and Dragon strikes, weekly and daily heroics, you'll see a steady stream of legendary engrams. Plus you'll be ranking-up your vanguard and Cryptarch level, which grants you legendary engrams some of the time.

Raids don't drop legendary engrams, but they do yield legendary raid items: armor, weapons, ships, and class items.

Sometimes you're flush and sometimes you're bust, and when you're up, it's never as good as it seems, and when you're down, you never think you'll be up again, but life goes on.

- Michael Scott