I'm not implying that whilst guests are loading staff should try and fill the empty seats... Staff should be batching ahead of time a train in advance. Whilst one loads, the next should be being prepared. I would consider it a personal failure if I had a seat empty, but I knew when to give up because I'd run out of time.
If you want an extreme example of how this can work, Oblivion at Alton can load two trains at a time, so a total of 4 rows. But there are 8 bays. The bays open in alternates, so staff have room to work in advance with the comparatively large number of people per row. It's rare you see empty seats on Oblivion, but this doesn't slow down the process at all.
Riddler's slanted station being to give guests a view of what's going on actually makes a tonne of sense, but the problem is that more than 4 people can fit in each row. So what happens is the gates open, and a group won't get on, because they're waiting for their friends in another row who aren't aligned, lacking the sense of let he group behind through. Or worse, all 8 of them are in one row then yell at the attendants for not allowing them to ride together. Another issue with not having batcher's is how do you deal with disabled guests? In the USA they just put them on stealing the seats of the main queue, but what should happen is rows are purposefully left empty in preparation for them, so no one feels conned of their seat.
I'm willing to bet these problems are less in the USA simply because American strangers actually talk to one another, but there is no way this **** never happens.
Another problem with overcrowding in batching areas is queue jumping.
The reason I love Nemesis Infernos batching area is that you enter higher up, giving a view of the station and everything going on. Then each bay only has room for 4, and guests cannot fill up any excess room anywhere. They filter in perfectly. So it doesn't need a batcher.