@Nephere What you are describing sounds like a syntax error in the dlclist.xml. When there is a syntax error in this file (or a addon DLC is messed up), the game will not load in any dlc content (cars, peds, maps etc) and only stuff in the base game. Symptoms of this is a quicker than normal loading time and unable to spawn dlc vehicles like the 811.
In coding, syntax makes a big difference and you probally made a mistake in the dlclist.xml as small as having " <Item>dlcpacks:/b12lang/</Item " instead of having "<Item>dlcpacks:/b12lang/</Item>" (all without quotation marks)
I'd switch back to the old dlclist.xml and see if the problem persists.