My testing method was to use a city guard in Whiterun and also my Companion. I would use the command "getav health" to determine their health before casting, then immediately on finishing casting I would verify their health. On Master difficulty (-50% damage) near point blank takes the city guard health from 340 to about 165. On Adept, the guard is instantly killed (as expected). For reference, Incinerate takes the city guard health from 340 to ~295 on Master and ~250 on Adept (as expected). Keep in mind these are approximate because I am not including the burn damage after, which adds another 40-50 (-50% on Master = about 20) damage from fire storm resulting in the guard having 141 life remaining on Master.
The further away the lower it gets to 270 being the lowest number (without the additional burn) I was able to achieve with primitive testing. I tested the same thing on several other NPCs with the same results. I know the description says it deals more damage at close range but this is actually a LOT more damage. Therefore it takes about 4 Incinerates to equal one cast of Fire storm if you are in close range, although the incinerates are still slightly cheaper and slightly more damaging. That's http://www.gamesas.com/index.php?/topic/1295613-equilibrium-spell-not-working-as-described/page__p__19517367__hl__equilibrium__fromsearch__1#entry19517367 spells in the game that I find the description not matching reality.