Despite the ongoing efforts to remove sluggishness, IMO weapon swapping is still not "instant enough", it often gets caught up with lag and is prone to error in a variety of situations (being stunned/knocked back/in the middle of other animations), which often causes unintended "double swaps" and generally takes dynamic out of the combat flow; it just isn't fast enough for many people. A few builds have even recommended to bring the same active skills on both bars to eliminate the time loss for weapon swapping, and I don't think this is the intended use for the two-bar system we have.
I think the problem with non-instant swapping is a technical one: there are passives associated with the different weapon sets, so your equipped weapon state always has to be in sync with the server which means we'll always have sort of an "input lag" so it feels a bit sluggish for people who are used to more "snappy" controls in fast paced combat. Therefore, I propose a middleground solution, which essentially disentagles input from the server communication.
Suggestion: Always switch only the bar clientside immediately (regardless of being stunned, current animations etc.) and allow us to queue actions on the secondary bar ahead of time, and have the actual weapon swap catch up in sync with the server as soon as possible like it does now.
This may very well be impossible due to their server tech (we wouldn't know the inner workings of course), but I do think there are quite a few people who would appreciate something like that. If we find numerous people to oppose it, it might probably be made an optional toggle even.