@Crowsfoot, I have always liked to deal with stormfiends using a very kill behemoth. Give a Carnosaur a Quicksilver Potion, heck even two carnosaurs, and watch them dominate the unit and come out clean. This is what I'd like to field against your friend.
Oldblood on Carnosaur 320
Quicksilver potion
Scar-Vet on Carnosaur 260
Quicksilver potion
Scar Vet On Cold One 100
Scar Vet On Cold One 100
5x Knights 120
5x Knights 120
5x Knights 120
Bloodclaw Starhost 100
1240/1500
You can play around with the remaining points, bit this is a hard hitting, slightly fragile, lost to murder the likes of stormfiends