Rotom-W @ Choice Specs
Trait: Levitate
EVs: 240 HP / 252 SAtk / 16 SDef
Modest Nature
- Hydro Pump
- Thunderbolt
- Trick
- Thunder
As it is right now, the core has some serious trouble with DrizzleSwim spam, due to Kingdra and Ludicolo easily being able to break through both of the Pokemon currently in the team's base core. This Rotom-W can take advantage of the opposition's potential rain (the biggest weakness atm) and exploit its now 100% accurate Thunder and crazy powerful Hydro Pump. Additionally, with the spread, it can live anything both Kingdra and
Ludicolo throws at them, and usually OHKO back (Ludi tends to run LO, which puts it in OHKO range).
Another huge problem is Landorus-T, as it will be able to switch into Tyranitar with ease and hinder it with Intimidate, avoid the OHKO from Volcarona and nail whatever it feels like (EQ will do tons of damage to Tyranitar and do respectable damage to Volcarona, Rock Slide will make Volcarona a mushed bug pie). Landorus-T cannot do much to Rotom-W, especially with the significant HP investment, and Specs Hydro Pump will KO the Landog back with ease.
It also has amazing offensive synergy with Volcarona; Volcarona hits the problematic Grass-types that Rotom-W despises and Rotom-W takes care of the evil Rock and Fire types that Volcarona has trouble with. The two of them together will also help put keep opposing weathers in check; Volcarona completely dominates Sun and Hail teams, whilst Rotom-W is a huge thorn in the side for Rain teams. Additionally, Rotom-W is only weak to one type, Grass, and Volcarona can draw these moves in with RP and usually take less than 10 percent damage due to the 4x resist.
Edit: Yeah, trick > HP Grass