Fallen Rayla is one of the most poorly designed cards in the game.

There's just so much antisynergy within her effect.

To make her worth it, you need a lot of tributes. A deck with a lot of tributes is best with Off The Books. But because this leader makes tributes cheaper, it actually makes Rayla WORSE! Name one other card that has antisynergy with it's own archetype…

She's also best used with big tributes, like Savolla. But Savolla is best used with Luiza, which completely cancels Raylas effect. So much antisynergy, it's infuriating. You basicly have to decide between Luiza and Rayla and Luiza is just better, hands down.

Honestly, Salamandra Mage is vastly superior to Rayla for less than half the cost and you can play up to three copies of him. He works with free tributes from Luiza (and can make Luiza's tribute free or even gain coins if you have two on board) or Rogue Mage and he actually synergizes well with the leader ability. He even plays for more points on deploy than Rayla.

The only somewhat viable use for Rayla is in double Salamander meme decks and that should not be the case for a headliner card of an expansion. Her whole design feels like nobody in the development team spent even 5 seconds thinking it through, yet alone tried her in a match.