Currently, the spell batching is a lot faster than it was back in Cataclysm, which was still a lot faster than back in Vanilla, which was still faster than in Classic before 1.13.7.
But I remember there being a setting back in Cataclysm, which you could use to be able to queue a spell cast up to 400ms before the cooldown or last casting time was complete. And the queue would work server-side, similarly to the spell batching we experienced in Calssic.
Maybe it would be a good idea to make a way to restore the option to customise that behaviour? It would be useful for the slow-paced players, as well as for those who prefer high graphics settings over framerate.
The queue did not work server wide, what you’re talking about is having the opportunity to pressa button (up to) 400ms before it’s castable and still have it cast when it is ready rather than spamming it.
As far as I remember, it did work somewhat server-side, but it was hard to notice because the server was still using the spell batching of about 100-200ms, the same as it was using back in Vanilla.
However, it was easy to notice on unstable connections. Back in the era of those newly-introduced 3G modems, there was a big difference between 400ms and 100ms.