Arcanine is a boss and has excellent stats for a mixed use.
If Physical sweeper:
Arcanine @ Muscle Band / Leftovers
Ability: Flash Fire
EVs: 252 Atk / 252 Spe / 4 HP
Adamant Nature
- Fire Fang / Flare Blitz
- Double Kick / Reversal
- Thunder Fang
- Iron Head / Morning Sun / Agility
Double Kick is there as a substitute breaker and coverage, Thunder Fang is there as a flinch and para chance and coverage, Fire Fang is a burn chance and STAB, or Flare Blitz for a more powerful STAB but with recoil, and the last is for whatever floats your boat.
If special sweeper:
Arcanine @ Power Herb
Ability: Flash Fire
EVs: 252 SpA / 252 Spe / 4 HP
Modest Nature
- Solar Beam
- Flamethrower
- Swift
- Agility
With a Power Herb you can hammer off that first Solar beam while they expect you to set up, Flamethrower is a reliable STAB, and Swift is for those stupid Double team users, Agility is self explanatory.
If used as a mixed tank:
Arcanine @ Focus Sash / Leftovers
Ability: Intimidate
EVs: 252 SpD / 252 HP / 4 Def
Hardy Nature
- Toxic
- Morning sun
- Dig
- Fire Fang
He has sufficient bulk to pull this off, and it would be rather unexpected, you set up with Toxic and then use Morning sun and Dig to keep yourself alive while they take ongoing poison damage, then you use Fire Fang for those stupid steel types that I love.