I rather wish the epilogue had had more in it, especially about the other characters, especially since she's had it written for years.

Maybe the fact that she'd had it written for years was WHY it didn't say much about the other characters. It seems like she'd decided pretty early on that Harry and Ginny would end up together, as well as Ron and Hermione. But maybe she didn't want to back herself into a corner with other characters before she'd written the other books.