Jean is pretty nice. The stats are pretty low but she comes with a low cost to use as well. At 16 power required she offers a smaller consumption than most of the better Rares. On top of that she has versatility with a Remarkably degrade to ATK and DEF all. This degrade will offer about a 7% debuff to her opponents.
Her final stats are to be determined but based on my estimation I would say she ends up right around that 6k attack and defense that Black Widow ended around.
Current value of referral cards is pretty low since people can create accounts for them and thus keep the market flooded, but referral cards are also currently the best way to skill up high level cards, so they still hold some when fused into their UR form.