Shockwave, Mass SR and Bloodbath all depend on the fight actually.
3s: If they're melees then go for Shockwave and Safeguard to peel them off of your healer. If they're casters (especially with a RDruid) then go for Stormbolt and Mass SR to reflect some CCs. Now I prefer Avatar rather than Bloodbath, all you need is to just CC chain their healer and burst down one of their dps, especially if you have another class with high burst too.
I'm not a high rated player and I play a panda (yeah I know its silly, but pandas are OP). I play with a class that can CC and use single target burst, as soon as the healer uses his trinket, I use Stormbolt, then pala uses FoJ and then I run close to stun him for another 5 seconds, this means he had a 10 seconds CC, I can still fear after that and my priest healer can also do it too. with Avatar you can actually pull a lot in the 10 seconds CC window. Let's say you're running with a hunter, you use Bloodbath and Stormbolt their healer, he will have the bleed damage which means the hunter won't be able to freeze him. If you wanna go for Bloodbath then you will have to be careful when using it.
Edit: If they're melees, you will try to peel them off most of the time so you can change Rude Interruption to Heroic Leap and Bull Rush to that one that stuns/roots 2 targets.