Different but equally deep
I think that The Heirophant and Lovers are more surface/shallow depictions of marriage roles than the deeper stuff that The Devil implies.
The Hierophant relates to a marriage's social conventions (i.e. religious and cultural rituals that acknowledge the union and the new position of the participants in the society). Which may, at first glance seem shallow/superficial, but on further examination can be quite deep. Traditions can have powerful meanings not just to a society but to individuals; and our culture can make it as hard to extraditing oneself from a marriage as the Devil's "addictive" energy. So, while the Hierophant's traditions can be "surface," they could, equally, be very deep, especially to religious participants who see such traditions as relating to their connection to the divine (a man's marriage to a woman being related to Jesus married to his church, for example).
Meanwhile, the Lovers is about how someone recognizes a twin psyche or spirit. What that recognition might lead to *after* the two are united isn't the purview of the Lover's card, but that doesn't make the card superficial. Again, it could be a very powerful psychic energy that keeps them together as strongly as that energy of the Devil.
Granted, these two cards *can* apply to participants in an arranged marriage who haven't met till the wedding. Not so with the Devil which has to be about an on-going relationship. This, however, doesn't mean that the devilish attachment is "deep" so much as difficult when it comes to ending it. Which is to say, we all have our favorite cards, but as cool as the Devil is, and as far up in number (Qabalistically that actually puts it lower down on the Earthly plane and farther from the esoteric), I wouldn't rank it as more deep or less shallow than the Lovers or Hierophant when it comes to relationships. The trio, I think, are different, but equally deep and complex angles on the topic.
