I am ok with having superclasses / class groups. I think it is better than having one Mage superclass while all other classes are individual. But I also think that
not having any superclass would be just the same. I only don't like much the "hybrid" approach.
While I say I am ok with the approach, I still don't buy the benefits at all:
Mearls said:
There are a few benefits to this approach.
It gives a framework in which we can add new casting styles and approaches to magic that are specific to settings.
It makes expanding the game easier, since we can create one list of spells for those classes.
It simplifies magic items, since something like a staff of power can refer to the mage. We know that any future classes included under the mage can still use that item.
First point, the "framework" is ok but it's not really needed. In previous editions if you wanted to add a new casting style, you'd make a new class. There is no problem with that. Some people seem to dislike having 20 classes in the game, but how is that different from having 10 classes, some of which have multiple versions so that the total is still 20?
Second point, it makes it easier only as long as it's really appropriate for that list of spells to be identical, otherwise it makes it harder. And no surprise, a few lines later Mearls admits that using the same list of spells for Wizard, Sorcerer and Warlock would be inappropriate...
Third point, this is ok if and only if you want magic items restricted to a subset of characters, like "only priests can use this item". But this is only one possibility, and by nature it defines something about the fantasy world which is not appropriate to every campaign. Overall I don't have much against this, but it's hardly important.
And a monk is a priest type, not a warrior and definitely not a rogue or trickster. A middling fighter with fixed miraculous abilities.
And here lies the real downside of adding another layer of categorization. As soon as you frame the categories, you want to use them, and they tend to force the game to conform to them.
Is the Monk more like a warrior, a priest or a trickster? Is the Bard more like a warrior, a trickster or a mage? Depends who you ask!
The point is, the Monk is a Monk, and the Bard is a Bard. Without superclasses, there is no issue, you just design them in whatever way you feel right. With superclasses, they are already puzzled about how to
make them fit into one superclass, a problem that did not exist yesterday, and they are tempted to force changes that weren't needed before.