I don’t think it’s too much. To me it comes off as
Cassandra with the popular suffix -iana (like
Ariana,
Eliana,
Liliana etc).
Cassian seems to be getting more popular for boys, so why not Cassiana for girls? Cassiana has some cool nickname options too. I personally prefer it pronounced as Kash-AHN-a, not CASS-i-ahn-a.
From your list I like Cassiana
Eve and Cassiana
Juliet the best.
**I love God far too much to be religious -
Jean Claude Koven**