Idea 1. Reassign Alt-Tab hotkey.

Instead of switching windows via Alt-Tab, one can switch by the same keys as in-game hotkeys.

For example, if the player uses "1" or "2" for damage, he/she can reassign Alt-Tab to 1 and 2. The WoW client sees 1 and activates a spell, the Windows sees 1 and switches to another WoW client. So to damage by 3 characters, he/she just need to press "1" or "2" three times. The same works for mounting, drinking, etc.

Moreover, this idea works for Interact-With-Mouseover and Interact-With-Target hotkeys. So there is no need to pressing switch when gathering and looting/interacting.

And finally, it works with mouse clicks. If switch windows by, let's say, right-click with a shift, the gathering of a node by 5 characters is just 4 more clicks!

Idea 2. Use the mouse wheel as a hotkey for damaging.

Rotating a wheel is much easier than repeatedly pressing a key. The turn causes the damage and the switch. This idea makes damaging by all (!) characters as easy as browsing internet pages.

Certainly, you have only two damage hotkeys in that case (wheel up and down). But paired with Gnome Sequencer addon, a multiboxer will have a good enough rotation.

How to reassign?

Personally, I use my own program for it (https://level-buddy.com/wow_switcher/). However, those who use programs like HotKeyNet or AutoHotKey can make a script for it.

Anyway, it works:

https://youtu.be/7l_yINgvtJw

I hope this will mitigate our current problems after broadcasting denial.