They do, synced and unsynced. This was added recently for ARR dungeons, I think either 5.25 or 5.3, but I've farmed glamour pieces in Sohm Al long before that.
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The Aetherochemical Research Facility doesn't even have loot drops.
Here's another one. Could inventory please make some sense when switching between computers? I used my laptop for playing when away from home for Christmas. I used the cloud settings feature for syncing my settings, and that always ignores inventory. So I figured inventory order is stored locally and sorted it out on the laptop. But then I returned to my computer at home and my inventory was messed up here! So obviously some part of it is stored on the server, but not enough that it could stay in order on both computers. Please make it either fully synced (preferred) or fully local. This hybrid behavior is infuriating.
I was feeling crazy, so I went and ran a couple of dungeons unsynced. Turns out we're both right. Leveling dungeons (that is, 1-49, 51-59, 61-69, 71-79) all guarantee drops based on your role. Patch dungeons (50s, 60s, 70s, 80s) do not drop guaranteed pieces. I think there might have been some miscommunication in there wherein I thought you meant all expansion dungeons didn't guarantee drops, and perhaps you meant only the end-game patch dungeons. Sorry for the miscommunication!
Still hoping to see some of these things addressed.... still peeved about the hunchback of Miqo'te Males LOL