I don’t know whether this is exclusively a Mac issue, but that’s what I play on. Briefly, I get to the login screen, where I am accustomed to using arrow keys to scroll through characters and then using the enter key to enter the game. But since the 8.2 patch, it’s like I’m not really “in” WoW until I touch the screen with the mouse — and even that doesn’t actually affect anything, it just brings the game to the front. At that point I can proceed as normal. This happens no matter what I do; I’ve tried tabbing out and tabbing back in, but the game isn’t active until I “poke” it with the mouse. It’s not a huge deal; everything else works fine. But it has never happened before the 8.2 patch, and now it’s happening on at least two of my computers. I’m only brining it up in case it’s a symptom of a larger problem.
Happens to me since 8.2 as well.
It’s happens for me as well since 8.2!
I’ve been experiencing this as well. It occurs both when I use the launcher to start WoW, as well as when I launch the game directly.
Ditto here on both of macs (10.14.5 Mojave on both). Basically I start up game (skipping the battle.net launcher usually) and though I can cut/paste into pw area, cannot type til I click using the mouse.
Same here with latest Mojave 10.14.6
For some reason (probably a bug) after 8.2 patch the game window doesn’t finish loading with focus. You have to click some where on the screen to make the window forward then you can do whatever.
Well you can paste into pw field but cannot type Enter without error noise. Also if you alt-tab and then click back (or alt-tab again), there is still the error noise til you click on the window. Would think that would get it back to ‘focus’, without the need to actually using a mouse to click it.
Perhaps this is just a way to mess up or annoy multi-boxers. 
Ive been getting this too…since 8.2.5 I think.