I didn't miss anything. As I said, I found both their interactions very plot based and Lady's arc to be tied directly to plot events. The Lady-Arkham dynamic was a major part of the plot, and with Dante, I should've specified that I meant their character moments together were exposition (which it usually was; their two big moments - Lady talking about her dad to him, and the Divine Library were both clearly made to tell the audience about what's to come or the give backstory). As for Vergil, I understand his design. Like I said he was great.
I feel like you completely missed my comment. I didn't say either was bad or poorly designed or didn't make sense. I said I felt nothing from either. Both just seemed like ways to get to the ending.
I'm not sure how that's missing the point unless you're saying that by feeling as though they weren't effective characters I somehow can't see them as well designed? They were good. I just don't like them, that's all.