The BannedAddOns.dbc seems to contain the baddons.wcf file (0x0014 to 0x01F7), which is extracted and put into Cache\WDB\<locale>\baddons.wcf at startup.
The newest baddons.wcf (from the current EU PTR Client) only contains "d41d8cd98f0b24e980998ecf8427e" (= md5 of an empty string) for all entries.
I think i was wrong with the last 4 bytes of an entry, these are now 0x0002 for all of them so they don't think they mark the last entry of the file. Maybe it's a version identifier incremented each time an entry is modified (pure speculation).
The unknown 4 bytes are now 0x49347A01 for every but the first and the last entry (which have 0x493479E8 and 0x49347AF9). This is the only thing that has changed comparing to the uploaded BannedAddOns.dbc from yoshimo. This one contains 0x49346BD8 for the first, 0x49346CE9 for the last and 0x49346BF1 for the rest. Maybe it contains a locale id.