Rey's the epitome of the glass cannon archetype. She does what she does, and does it very well. She's great on offense (go figure), but the AI handles her very poorly. So if you know how to handle her, you'll do fine. Her high damage comes at the cost of:
--Low HP
--No leader ability
--Low Tenacity and a loses up to 23% of her damage when debuffed.
No need for a rebalance. The reason you see her so often is that she does the most damage, reduce that damage and you're going to have to reduce those drawbacks to compensate and you'll wind up in the same place you started.