I still can't help but wonder if there will be a signature feature that will be available to every class group is defined by having access to "blank." From the first UA, we know they plan to use Class Groups to determine what items you can "attune" to or which feats you can access. But it's starting to look like there will be signature ability as well.
Experts: "Expertise"
Priests: "Channel X"
If correct, that's why Paladins are considered "Priests," and Rangers and Bards are "Experts."
So far, we can only speculate on what the signature feature of the other class groups might be. However, they haven't used access to "spells" to differentiate the groups so far (otherwise Bards would be "Mages," and Rangers would be "Priests"), so I wonder if they've come up with a signature feature for both of the other 2 "class groups" as well.
I guess we'll find out in a couple weeks, but does anyone want to speculate wildly before then?