I think that the best names for the class groups depend on what they're actually supposed to mean. Right now there's sort of a mix of different criteria suggested at, including mechanical similarity, thematics, party role, similarity to one of the "core four" along various lines, and general silhouette. Additionally, right now the class groups seem to be based around the idea that Fighter/Rogue/Wizard/Cleric is a natural way to clump classes, something that's not necessarily true regardless of which axis you're basing your classification on. If the classifications are based on what party roles you most ably tend to fill, then I think that the names that suggest specific power sources aren't so hot. If they classifications are based on your thematics, then the currently given descriptions seem too narrow.
I do think that it's important for the names to be as broad as possible. It probably won't always be possible, but the more it can be the case that "A [classname] is a kind of [classgroup]" is a sentence that sounds right in normal language, the better. For example, "A Paladin is a type of Warrior" sounds right in english. That works out pretty well. Ideally, the names should also reflect what the groupings actually mean. For example, "Leader" isn't a good name for the 4e Leader role, because while a 4e Leader may or may not be a leader, what leader actually means is "Supporter". Without knowing what axis the groups are actually dividing classes along, it's hard to know what good names for them are.