Okay, not going to quote things for time's sake. So just scroll back a little if you want to get context.
1) HPFJ does have the Express queue. It has its own Portrait Gallery, then the tracery hallway, Dumbledore's Office, DADA Classroom, Gryffindor Common Room Vestibule, Gryffindor Common Room (Queue Control.) So minus the Portrait Gallery, its just the tracery hallway and forward. They will not use Express for the foreseeable future. As aforementioned, it floods the rest of the Express.
2) RockIt will never use it. 12 people every 30 seconds (at 6 trains, which is near impossible), bearing no belt stops, does not lead to capacity enough to move two different lines. There's a reason Single Riders for HRRR can match the normal wait time.
3) Remember, during Spring Break WWoHP had to go to Land Control. If you think that London won't send both parks back into Land Control, you're sadly mistaken. Expect the Express Lines to be useless during that period. Also, Gringott's may be using a Merge line instead of split Express. Universal has been trying to turn all the coasters into merge lines. I.e Hulk and Dragons Challenge. Heck, even Spider-Man briefly (two days) attempted to use a merge line.
4) Transformers will suffer the same problem as Spider-Man. 2 loading spots at a time, manual car moving, ~21 second dispatches. The Express line WILL be 45 minutes. They can increase the ratio of Express "cars" to regular ones and it'll make the problem better, but only for Express guests. Even Despicable had 45 minute Express waits when it first opened. They had to keep cutting off the Express line because of the demand.