Got the same issues. These are shadows it seems. I had the lowest shadow settings in WoW. When i changed it to 1 higher, most shadows went correct. But you still see sometimes those black boxes(shadows) on the floor. I think we need to wait until this is fixed.
There’s a black box under every character that you can get rid off by turning the Shadow Quality up higher than low but there’s also another effect with the same affect. It’s tied to some effects like the swirl thing they use all the time. They can stack on each other so it makes it hard to dodge stuff.
(EDIT: Basically you get the same black box around the swirl but it’s bigger than the ground effect should be and it stacks with other ground effects.)
I’ve messed with all the graphic settings and nothings changed it.
I haven’t been able to find anything on the official forums but I can check again in a bit.
Same problem here. Raising the Shadow Level in Graphics Settings fixes some of the problems (like the shadow on player characters), but there are still problems with graphical effects on some boss abilities in the raid.