Hisuian Arcanine

Hisuian Arcanine is an upgrade over Magcargo, which....isn't saying much. A 232 ATK stat and moderate moveset isn't terrible, but leaves more to be desired in order to topple the current leaders in the Fire and Rock typings. Hisuian Arcanine's weaknesses makes it a poor choice for gym defense. 

Best PvE Offensive Moveset

• Fire Fang pairs well with Flamethrower to fulfill a Fire-type attacker.
• Snarl should be used by Dark-type Pokemon
• Rock Smash is a suboptimal move. 
• Rock Slide lacks synergy in most scenarios. 
• Wild Charge is powerful but is recommended for Electric-type Pokemon.
• Crunch likewise performs better with Dark-type Pokemon. 

Best PvE Defensive Moveset

• Rock Smash is arguably more favorable for defense with its high base power.
• Fire Fang hits hard with STAB, but is resisted by Water-type attackers.
• Snarl is resisted by common Fighting-type attackers.
• Wild Charge is arguably the best for defense, threatening Water-type attackers. 
• Crunch can be spammed frequently on defense, making it generally useful. 
• Rock Slide is unresisted by Water attackers, but Fighting-type attackers are very common.

Snarl is preferable for its high energy generation, letting Hisiuian Arcanine access its Charge Moves sooner. Fire Fang is the polar opposite, boasting powerful STAB damage with poor energy gains. 

Wild Charge is the strongest Charge Move available to Hisuian Arcanine, though its harsh self-debuff makes it tricky to use. Rock Slide benefits from STAB, offers useful coverage, and costs a moderate amount of energy. Crunch lacks STAB and its typing isn't particularly useful to coverage Hisuian Arcanine's weaknesses. Flamethrower is surprisingly not impressive despite synergizing with a Fire-type Pokemon, due to its moderately high energy cost, but can still be chosen if needed.