Agreed. Although, people shouldn't be thinking too defensive when they think synergy. Sun teams still need to be very offensive when they play, as they need to use momentum to sweep.Sunny Day teams are made for synergy, Rain teams are meant for sweeping and revenge killing.
The other reason Rain Dance outclasses Sunny Day is because Rain Dance gets Electrode as a potential lead. Funnily enough, a Sunny Day team with the sun up messes up a Rain Dance team much easier than vice versa.The reason Rain Dance outclasses Sunny Day is because the abuser get their stab boosted, and that stab is a much better offensive attack in the metagame.
Not necessarily. Don't get me wrong, I love SD Tangrowth since it is a complete wrecking ball. However it can be a little harder to pull off in this metagame with spikes and priority moves kicking around. Sleep Powder is fine for incapacitating a threat. I use Synthesis to make him a bulkier check to guys like Rhyperior and Torterra. Having Swords Dance on Tangrowth is good, but not having it isn't bad.Also, there's no Swords Dance on that Tangrowth. This is a Bad Thing.