I love tarot, so this is a pretty interesting topic.
I'm adding my thoughts with some thoughts by people on tumblr that did a cool breakdown:
Dorian- Temperance
"Temperance indicates that you are learning to bring about balance, patience and moderation in your life. The card reflects that you have a clear, long-term vision of what you want to achieve. Temperance can also reflect a period of self-evaluation in order to re-examine your life priorities. "
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Sera- the Star
"The meaning of the Star Tarot card suggests that you have endured life’s challenges and have been through a difficult time but you are now open to healing and transformation. Your ability to let go of damaging memories has been strengthened by contact with your true self through these difficult times. The Star Tarot card also indicates a generous spirit. You want to give or share your wealth with others to help transform their own lives. You have an open heart and you now want to give back the blessings you have already received so that others may benefit."
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I think Vivienne could be the High Priestess, I could also see her as the Chariot card:
"The Chariot represents conquest, victory and overcoming opposition through your confidence and control. On its most basic level, it's about getting what you want. It implies war, a struggle, and an eventual, hard-won victory over enemies, obstacles, nature, the uncertainties inside you. The Chariot is a card of contradictions. It's about sidewise battles, yet also about full-speed ahead. It's about the hard exterior and the soft interior, the light and dark, the water and the shore, moon and sun. It is the Sphinx, which is also often a symbol of Cancer, the lion and the man united, a mystery." A mystery sounds a lot like Viv, since she has a secret agenda.
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I can see Iron Bull being the Heirophant.
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I think Cassandra is Death, her card and the death card look very similar and she's from Nevarra, a country that has a lot of interesting ideas concerning dead people:
Death: "Death is symbolic of the ending of a major phase or aspect of your life that may bring about the beginning of something far more valuable and important. Similarly, it indicates a time of significant transformation, change and transition. The card contains elements of a sudden and unexpected change. Death is an indication that you need to learn to let go of unhealthy attachments in your life to pave the way to a fuller, more fulfilled life of deeper meaning and significance."