Doryuuzu is great or at least you can't deny it isn't good. I played lots of matches with Doryuuzu and it was rarely disappointing me. In sand, (next to) nothing outspeeds it, 135 base attack, STAB on EQ, reasonable 110/60/65 defenses and immunity against TW and Toxic makes it one of the best sweepers you can dream of.
Doryuuzu @ Balloon
Ability: Sand Throw
EVs: 252 Atk / 4 Def / 252 Spd
Nature: Jolly
- SD
- Earthquake
- Rock Slide
- X-Scissor
Hands down, Balloon is the best item on Doryuzuu. Dory resists most attacks that are usually paired with EQ, it can get a free switch in, Spikes immunity, not revenged by other Doryuuzu who win the speed tie and the not existing yet ScarfDitto. These advantages overshadow the fact that Dory loses his Balloon when hit by an attack.
Max speed is important for forcing the speed tie against other Doryuuzu. It's fundamental, because you can't rely to have Balloon always on Doryuuzu. Also, Doryuuzu is always useful. Early and mid game it is one of the best revenge killers and lures in bulky waters and end game it cleans the opponent's team.
Spikes are essential, especially when you use Balloon over LifeOrb, as +2EQ won't OHKO all bulky waters / grounds. So, Nattorei is a great team mate, although they share the same Fire / Fighting weakness. Early and mid game Doryuzuu acts as a revenge killer and it will lure bulky waters and bulky grounds. Yeah, free switch and Spikes for Nattorei. Doryuuzu can revenge kill the Pokémon that can set up on Nattorei, making Nattorei viable for offensive teams. Nattorei also can deal perfectly with RD teams. So, this duo is viable despite the not so good type synergy.
There are just some few counters to Doyuuzu. Don't expect to outspeed it in sand, so Scarfers are not able to deal with Dory. So, you can only rely on changing the weather or priority, which Dory really hates. MachPunch Breloom is the best switch into Dory, as it resists Dory's usual attacks and Technician MachPunch is strong (yes, I know that Technician Breloom doesn't exist yet, but it's great). Mach Punch Ropushin, Aqua Jet Azumarill and Vacuum Wave Lucario can also revenge kill Dory easily. Balloon users that can easily take Dory's other attacks can also deal with Dory.
So, ScarfShandera with ShadowTag (blah, know it doesn't exist yet) can also switch into fighting priority and get rid of them easily. Shandera lures in Pursuit Ttar for free turn for Dory and bulky waters for Nattorei. It's really cool for getting rid of Pokémon that can prohibit a Dory sweep.
I see little talk about it, but Doryuuzu is now one of the best, when even not the best Spinner in the game. It's the fastest one and there are few ghosts that enjoy switching into strong EQ.
Just my two cents. A great Pokémon. No doubt.