I don't think Lantern needs to be TVMA either, but I'm not complaining if it means Guy can say whatever he wants. MA doesn't inherently mean it's going to be Game of Thrones, either. It's mostly just giving a show the freedom to do what they want without worry of censorship. And sometimes boils down to just a matter of "mature themes."
But JLD? I'd have very little interest in a PG-13 JLD. You say that Constantine/Hellblazer should be TVMA, but its the same character in both shows. I don't want to get a sanitized Constantine just because he's on a team. And I want the horror to be able to go as far as the team wants to take it.