Okay something I noticed in the Dean/Cas scene in 4x21 is that they're being visually paralleled with each other;
Which is happening because they're circling each other, physically yes, but conversationally too. Dean is chasing answers and Cas is evading him, but at the crux of it, they're both participating in a conversation they do not want to be having but see as their only choice. Dean doesn't want to hand over allegiance to heaven but in order to keep Sam from destroying himself, the angels are his only effective 'ally' left. Cas doesn't like having to withhold information from Dean, he already knows that they cannot stop the apocalypse, that he will free Sam shortly after this conversation, that this is essentially coercion, but he cannot defy his superiors because he's afraid (very recently tortured back into submission). They're both pawns being played in the grand scheme of the apocalypse, the difference being that Cas has a better idea of the picture than Dean, he has more power, that's why it's almost as if Cas is leading while Dean follows, like he's the dominant partner in their dance, because he is essentially leading Dean on.
