Astra

Astra usually isn't used due to how overkill it is. It's only really good on end-game maps because the enemies have super beefed up stats in Lunatic and Infernal mode. Give her something like Draconic Aura or Dragon Gaze.

I wouldn't use it at all, unless you have two Infranty Pulse unit nearby. Great for Arena if planned like that: Prep up the Astra-Enemy Phase unit, Bait an attack, Watch the Enemy regret their decision.

Keep in mind that Gronnblade increases cooldown count, so even with QP it'll still be a 4 turn cooldown. By then, Nino's probably killed or at least maimed everything on the map, lol. Glimmer is really good on her now, though.

Back on the topic of Astra in general... IDK, the lower cooldown certainly makes it an option now, but the "adds 150% to damage dealt" thing is still unreliable. Nevertheless, it might be worth trying out sometime. Just not on Nino.

Definitely don't use it with gronnblade, the special count increase just makes it not worth it.