This is very high risk high reward, there are a multitude of reasons why
Taunt
Taunt is extremely common in doubles and will prevent you from setting up Dual Screens and Ddance
Tyranitar
The two Pokemon you open with can easily lure Tyranitar in, who can also take away your rain with sand
Fake Out
By flinching your leads it can throw off your screen balance
Intimidate
Upon seeing your Gyarados has Ddance, your opponent will attempt to hinder it, and he/she can do this by lowering it's attack
Paralysis
Klefki and Thundurus are rampant, and thanks to prankster they can paralyze you no matter how fast you are, and they are common taunters
Sleep
Sleep from the likes of Amoongus, Breloom and others is also extremely common, and can hinder your water type sweep or support set up
Basically, what it comes down to is that this takes 3 turns to set up and you can't have any problems arise in these three turns, which is practically impossible. Your opponent will have three turns to cripple and damage you or even potentially set up and stronger counter offensive. It is best to refrain from offensive set up in doubles except in a few cases, and this is not one of those cases.
Hope this helps