Originally Posted by
Glyphtics
You should use Simcraft with a 240 second duration for Butcher DPS. Ideally you'll be within 5% of that number. Ballpark I'd say you should be doing around 22k - 24k DPS depending on how good the DPS in your guild is (fight length).
My guild facerolled through heroic, so I didn't deviate from EM / PE / LM, however for Mythic:
Kargath : EM / PE / LM
Tectus : AS / UF / LM
Butcher : EM / PE / SE (FET Glyph)
Brackenspore: EM / PE / LM
Ko'Ragh : EM / PE / LM
Imperator : AS / UF / LM
Storm Elemental and Elemental Fusion are incredibly underwhelming, and if you have the Lucky Double Sided Coin, EM / PE is a very very strong combination. Liquid Magma is mandatory for any fight with AoE or cleave, and you can delay your Storm Elemental on Mythic Butcher to line up with Coin for more DPS.