if you are using KJC on horridon you are doing it wrong.

Not only does MF allow your rain of fire to hit everything and give insane ember generation, it also allows you to effectively Fire n brimstone aoe the adds even when they are slightly spread out, and with clever kiting of your Fixated Direhorn, you can get it so that you can just spam aoe the adds that are up, and at the same time knock back the Direhorn whenever it gets close to the mobs you are aoeing. For progress run High mastery + Sacrifice and focus on aoe'ing down the adds, using chaos bolts on High priority adds (Dinomancer/priests) and havoc Shadowburn everything you can. Shadowburn is your friend on this fight, Rain of fire with MF is giving you insane embers and you can just go Cray Cray on Sburn spam when mobs are low.