>>16427336To be honest, it's more like this...
Wash > Cut > Heat > Frost
Before I continue, not that the big thing about all the Rotoms generally is you Volt Switch constantly. Stealth Rock damage hurts a lot when you keep reentering, even if you use Leftovers or Rest.
Waters's only weakness is Grass, and it doesn't take bonus SR damage. Grass, while it has three more weaknesses, is also not weak to SR damage. Fire has the most resistances out of all of them but takes bonus damage from SR. Frost has very few resistances and almost as many weaknesses as Grass.
In this meta Wash and Fire are very nice because they resist both STABs of Talonflame. Unfortunately you're going to see SR a lot, so without removal he's going to be forced to stay in or take constant damage.
Personally, I've had a lot of luck with Mow, but it depends a lot on your playstyle and what you're aiming to achieve. The Rotoms can fill most any role you want, you just have to be cautious with Volt Switching.