Gray has been killin it on Tempest Trials and I love it
the buff he gets for being a bonus unit is insane, he doesn't even take damage from most enemies because of his defense stat and he makes Sonya so much easier on the final stage. I've been able to clear the highest lunatic level without losing a unit of my team up until the 7th map with this crew. not to mention that Zanbato, while not really useful in arena meta, is absolutely killer in the computer generated levels where cavalry units are common. I'm pretty happy! Gray was one of my favorites in Echoes, so I'm really glad that I'm getting great use out of him and he's become a mainstay for sure.
speaking of teams, what have you guys been running in the trials? I've been using Reinhardt (+atk -spd, with Dire Thunder, Reposition, Luna, Death Blow 3, Lancebreaker 3, Spur Attack 2), Nino (+spd -hp, with Gronnblade+, Draw Back, Moonbow, Fury 3, Desperation 3, Hone Attack 3, Breath of Life 1), Gray (+def -hp, with Zanbato+, Swap, Bonfire, Wind Boost 3, Vantage 3, Sword Valor 3 (which I mainly just had because I've been grinding sp for Ike)), and Ninian (+res -spd, with Light Breath+, Dance, Speed +3, Escape Route 1, Hone Attack 3). This is my arena team as well, only difference being I swap out Gray for Ike. Who I'm still building... sets are expensive. but he's coming along. I feel like I'm doing decently for a f2p.