Well, Mamoswine with Superpower looks like it could steamroll through this team. You have 3 ice weaknesses and it looks like you would be screwed if you lost a weather war with rain.
Checks rain and Mamoswine while giving better offensive and defensive synergy at the cost of rocks and phazing.
That still leaves Volcarona with the job of dealing with Weavile though.
Also, why Tangrowth? All you said was "I prefer it". You're gonna need more than that to get a good rate in response.