if Fire is so perfectly well where it is right now, bring everyone else to the same numbers then. Why shouldnt EVERYONE be in the middle of the pact? All specs should be equal, no? Going off a basic simcraft - Fury warriors at around 880k, Fire mage at around 620k. No problem, just cut off 260k DPS from Fury warriors and apply the same to everyone.
Except then you have boss mechanics, addons, lag, kill times, zergs, player skill, effort/dps, cheesing mechanics, people dying, raid comps, etc. and the fact that you are balancing at EXACT legendaries and EXACT ilevel, so what you have in the sim in that case will be very different compared to what you will see in actual damage meters, except for the last months of the expansion.