I am in Onslaught Harbor, doing the quest “Intelligence Gathering” Collect keys and open the foot lockers for the documents. I have opened over 40 chests not exaggerating, and no documents in any of them. I have abandoned the quest and re picked up and looted new keys, but there are no documents in any of the chests. I doubt this is intended.
There are two types of chests. They have the same name, but one has documents and the other does not. If you are on the quest you can tell the difference because the document containing chests have a Quest Sparkle effect to them. This is not to say anything about whether or not there is a bug, just a way to see which chests have the documents in them.
hm interesting, I went into all the buildings and all the boats, kill my way inside the huge chapel, never saw anything like what you described, not to say you aren’t right, but I was there almost 2 hours before I gave up.
I also had this issue, ended up abandoning the quest. Like Ryanone says I didn’t know there were 2 types of chests though, maybe I wasn’t looking for the right stuff.
Only the chests that sparkle will have a document in them. Even when you know what to look for, they’re few and far between. The quest is 
In my opinion, this is the absolute worst daily when more than one person is doing it. The respawn rate of “openable” chests are ridiculous and you can easily end up spending over half an hour doing it. If I spend more than 10 minutes after I have already completed my other two dailies in that area I just don’t do it and go back the next day. Whoever set the respawn rate should diaf.