I've done PE's not capped and not gotten anything. They're RNG like everything else afaik. 30 patrol missions in 1.5hours? Maybe if you've got a fireteam doing the right ones. Otherwise you can get maybe 3 every 10 minutes at best and more realistically like 3 every 15-20 minutes. You can complete bounties doing strikes or patrols for most shit.
Pretty sure Tiger strike playlist nets you one blue engram, one blue armor, and an additional chance at an engram plus currency. Some one did a 55/55 pre-and-post patch loot table for Tiger strikes:
Loot from 110 Vanguard Tiger Strikes BEFORE and AFTER patch : DestinyTheGame
Basically it looks like with drops and rewards you're looking at an average of 2 engrams per strike. That's one per 7-10 minutes. That's not too bad at all.