OK. First, I'll show you the Marilland teambuilder.
(I didn't include Wobuffet because I didn't think he would help that much with resistances and such.) As you can see, you've got a pretty large weakness to Ground attacks. This will be the foundation of my answer.
TYRANITAR:
I know from experience, Dragon Dance just doesn't work. You'll be needing 3 DDs to outspeed any Scarfers, especially with Adamant. I'd trade Dragon Dance for E-Quake.And if you do that, replace the Speed EVs with HP ones.
New Set:
Titanic Tyranitar (Tyranitar) (M) @ Leftovers
Trait: Sand Stream
EVs: 4 SDef / 252 Atk / 252 HP
Adamant Nature
- Earthquake
- Stone Edge
- Crunch
- Superpower
GARCHOMP:
That set looks good, but I'd recommend trying out Scarfed Outrage. That thing is a beast under sand, especially with its above-average Speed. One of Garchomp's best niches is outspeeding Palkia. Forgot nature and EVs btw.
New Set (recommended):
Land Shark (Garchomp) (M) @ Choice Scarf
Trait: Sand Veil
Adamant/Jolly Nature
EVs: 252 Atk / 252 Spd / 4 HP
- Earthquake
- Stone Edge
- Outrage
- Fire Fang
ARCEUS-ROCK: Try a more defensive route.
New Moveset:
Arceus Rock @ Stone Plate
Trait: Multitype
Timid Nature
EVs: 252 HP, 252 Spd, 4 SAtk
- Judgement
- Calm Mind
- Will-O-Wisp
- Recover
DIALGA:
Great, might want to consider Draco Meteor however.
GENESECT:
You need Flamethrower to hit Ferrothorn, the biggest threat to you in sand. Also need Hasty, otherwise base 90s will outspeed you Scarfed Positive.
New Set:
Genesect @ Choice Scarf
Trait: Download
EVs: 4 HP / 252 SAtk / 252 Spd
Hasty Nature
- Flamethrower
- Thunderbolt
- Ice Beam
- U-turn
WOBBUFFET is a gimmick and needs to be replaced.
Giratina-O @ Griseous Orb
Trait: Levitate
Modest Nature
EVs: 104 HP / 252 Def / 148 SpA / 4 Spe
- Rest
- Sleep Talk
- Calm Mind
- Dragon Pulse
this takes care of your ground weakness.
