+Atk / -Spd Ayra still usable?

Yes she is, she’s not as optimal as she could be of course but she’s still Ayra. First of all +Speed seal helps both her doubling potential and her damage(Regnal Astra) a lot. She comes with Threaten Speed, so with the +3 Speed seal and Swift Sparrow it’s still a virtual 49 on initiation. If you like enemy phase, +Spd Slaying Edge and Fury might be your best choice. Dual phase presence and the possibility to set up Drives/Spurs easier. You could even run the DC Wrath build, with that +attack, Regnal Astra and Wrath you’re probably going to kill almost every common mage nowadays. If you’re going for a melee duelist build and are willing to provide speed buffs(maybe a Hone+a Drive) you can also go for Close Defense to help her survivability(Slaying Edge is better here for the 1 turn Regnal Astra here since to activate CD you have to bait and not engage).