What to do with my +att -Spd Y.Tiki?

Yes. 30 neutral speed, while second fastest among dragons (Corrin and Fkana are faster at 34), is nothing to really write home about and a bane in it is still more than serviceable for the standard Steady Breath+Quick Riposte+Aether high-end dragon build. +atk is also one of her best boons so, in that regard, you got a pretty solid IV spread for an enemy phase dragon.

The speed loss hurts Ytiki's player phase potential more than anything, so that might be a deal breaker depending on what role you want her to fill, but as a standard dragon +atk -spd is more than serviceable.