I happen to see you have 2 sweepers and 1 staller. I may have not played for 2 years, but I still remember alot of things about pokemon. So you're using it ingame. You're using Gengar as a sweeper. Focus Blast is powerful, and might be useful sometime, But it has bad accuracy. I guess you should use Brick Break. It might be not as powerful as that but at least it can break screens and also is more accurate than Focus Blast, but it's your choice. The focus sash is useful, and you're right. It is very fast, but you can use it if the foe will K.O Gengar in one hit. I think you're better off with a Sitrus Berry or some Leftovers. And don't change Sludge Bomb with Sludge Wave. Sludge Bomb is better with poisoning but Sludge Wave may be stronger, but only a little. You better stick with Sludge Bomb. Or you can also change Thunderbolt with Protect or Will-O-Wisp. Your choice.
Haxorus is perfect for this job. Nice moveset, perfect item for Outrage, great EVs, and most of all, nice pokemon. You'll be okay with this guy.
For Ferrothorn, he's good too, you just don't have EVs. I recommend your EVs to be like this: 252 HP/ 42 Def/ 172 Atk/ 42 SpD/. He's too slow already, and it's okay for it to be like that. Relaxed is good, +Def -Spe, and helps whenever a good Physical Sweeper is your foe. So basically, this is how it'll look like:
Gengar @Leftovers/Sitrus Berry/ Focus Sash
Trait: Levitate
252 SpA/252 Spe/4 HP
Rash Nature
Moves:
- Thunderbolt/Will-O-Wisp/Protect
- Shadow Ball
- Focus Blast/Brick Break
- Sludge Bomb
Haxorus @Persim Berry
Trait: Mold Breaker
252 Att/252 Spe/4 HP
Naughty Nature
Moves:
- Dragon Dance
- Outrage
- Earthquake
- Brick Break
Ferrothron @Rocky Helmet
Trait: Iron Barbs
EVs: 252 HP / 172 Atk / 42 Def / 42 SpD
Relaxed Nature
Moves:
- Gyro Ball
- Power Whip
- Toxic
- Protect
Overall, you have a good team.There. That's what I suggest. I hope this helps!