I have given to the Cryptarch like 20 Legendary Engrams, and as for now, I only have succeed in obtain only one legendary item. 1 in 20!!!
Really, this doesnt work, it turns meaningless the farming.
If you don't want to be very easy for the players to obtain legendary loot, ok, it's fine. Reduce the drop rates, but make sure that each time we got a legendary engram, it's a legendary item what we are going to obtain from the Cryptarch
-
Save those engrams for later, and work on leveling up your reputation with the Cryptarch, the higher your rep the more likely he'll decode a legendary item for you. However it is not guaranteed that the legendary item will be one that your classed character can equip though. I'm a Warlock and I've decoded two Hunter equip items.