Is my Battle Tree team good?

[AxelTheInkling]

Pheromosa
Item: Focus Sash
Ability: Beast Boost
-Lunge
-Brick Break (TM)
-Poison Jab (TM)
-U-Turn (TM)

Xurkitree
Item: Magnet
Ability: Beast Boost
-Thunderbolt (TM)
-Energy Ball (TM)
-Volt Switch (TM)
-Dazzling Gleam (TM)

Silvally-Fire
Item: Fire Memory
Ability: RKS System
-Multi Attack
-Swords Dance (TM)
-Crunch
-Punishment

 

[Somewhere_]

Your team has a lot of offense capabilities, so you might want to consider a defensive pokemon.

 

[Nah]

What are their natures and EVs? Those need to be good too if you wanna make it through the Battle Tree.

You also want Ice Beam (over Lunge) and High Jump Kick (over Brick Break) on Pheromosa. The coverage Ice Beam will give you is very good (Dragon types, all the Ground types not Grass weak, all the Flying types not Electric weak, etc), while you need the raw power of High Jump Kick, even if it doesn't have perfect accuracy (the game will screw you over with other hax anyway).