I actually think Excadrill is the best Mold Breaker right now for a number of reasons: Typing, access to a speed doubling ability,
Probopass is indeed interesting - its typing is still horrible though despite handling Talonflame and co well (most of the best fire types - the Zards for example, get access to Earthquake / Focus Blast).
Heliolisk does seem to be a neutral weather abuser, as is Goodra, Stoutland, Excadrill etc. That being said, I do believe that despite not getting direct boosts unlike Water, Flying and Electric types move-wise, that grass pokemon do have a reason to use rain as their supplementary weather due to reduced damage from fire moves. As I mentioned - Victreebel, as well as Venusaur - both have access to Weather Ball (it can even be a semi useful tool for Venusaur to negate its damage via rain before mega evolving, but an offensive Venusaur should use its hidden ability and pave the way for a different mega on your team anyway)
Snaquaza mentioned that Claydol with bug Levitate is one that completely blocks Voltturn, which is interesting although... it's Claydol (How good it is depends on how this meta pans out anyway).
Tagging Pikachuun and Slayer95 to gain some insight as to how this can be coded. The IVs don't seem optimal due to the issues with Fairy and Normal - and despite comments I'd prefer not to ditch the weather abilities unless completely certain about coding issues involving them.
Probopass is indeed interesting - its typing is still horrible though despite handling Talonflame and co well (most of the best fire types - the Zards for example, get access to Earthquake / Focus Blast).
Heliolisk does seem to be a neutral weather abuser, as is Goodra, Stoutland, Excadrill etc. That being said, I do believe that despite not getting direct boosts unlike Water, Flying and Electric types move-wise, that grass pokemon do have a reason to use rain as their supplementary weather due to reduced damage from fire moves. As I mentioned - Victreebel, as well as Venusaur - both have access to Weather Ball (it can even be a semi useful tool for Venusaur to negate its damage via rain before mega evolving, but an offensive Venusaur should use its hidden ability and pave the way for a different mega on your team anyway)
Snaquaza mentioned that Claydol with bug Levitate is one that completely blocks Voltturn, which is interesting although... it's Claydol (How good it is depends on how this meta pans out anyway).
Tagging Pikachuun and Slayer95 to gain some insight as to how this can be coded. The IVs don't seem optimal due to the issues with Fairy and Normal - and despite comments I'd prefer not to ditch the weather abilities unless completely certain about coding issues involving them.