I have no idea what the icons highlighted with a red box are; I assume they are for the different schools. Tooltips for these would be awesome.
For sure there are many Tool Tips missing.
But if we look the the ones we have, they are aware of must to have them.
We got the interaction Tooltip above the Actionbar, we have several tooltips of skills and some already available descriptions, so i think it is driving the right direction.
I am expecting the UI will change much over the time.
Look at this Ability Book from the Knowledge Spotlight, it looked different, but gives an idea how it could look like at the end. .
I guess it is much busywork to fill them all
As for this icons, that are filters for now, if you don't want to see some skill class, just click the icon and hide them this way.