I no longer see anything track-able in the ATT mini list when I'm on the Darkmoon Island, on any of my characters.
I've noticed the problem just now, it was working correctly last Darkmoon Faire (first week of August), which probably means the issue was introduced by one of the latest updates.

Here's what I see on the mini list comparing to what is shown on the main list - as you can see, I have some uncollected achievements and items shown on the main list, yet nothing on the mini list. In fact, I know I have lots of other Darkmoon Faire things still missing, mostly vendor stuff, and they were correctly shown on the mini list up until this faire.

Here's what my ATT options look like, and I should mention that I did not touch any of them for a very long time. It does not look like any of my filters are causing the problem.

When the debug mode is enabled in the ATT options, I see all uncollected things on the mini list.
Let me know if you need any additional information from me.

Ok, that brought my mini list back, thanks.

Something else I've noticed: if talk to one of the Darkmoon Faire vendors that still has some items I am missing, these items are correctly indicated as not collected on the tooltip:

At the same time, a tooltip on the same vendor does not show there's anything to collect at all:

Unobtainable tab > Seasonal Items (top of page) > Darkmoon Faire