Well, if we're just talking about looking alike, that's a fault of the various artists, who just don't know how to properly make their faces distinct, which was also a fact during the previous series, since the DM looked the same there too, most of the time. Having a similar style doesn't mean they should look like twins.
As for characterization, well, yeah, I agree. I mean, I don't even recall if they've ever been refered to by name in this series. The closest thing to any insight we've seen into their character was during the brief argument they had during the Killmonger fight. But, frankly, that's the fault of the writer. That can be fixed in upcoming stories, without having to change their looks.
I'd like to see some more of what their actual role is now. Hudlin's Wakanda doesn't appear to have the same tribal conflicts as the previous version, yet Storm still refered to them as T'Challa's "Wives in Training" back in the Wild Kingdom crossover. And now that T'Challa's married, why are they still around? I guess they're essentially the Wakandan version of the Secret Service, who bodyguard the King. But how does Storm feel about them?
These are all issues that should be explored more in the future, but, really, all of the supporting cast could stand to be fleshed out more.