Ok, no one has deigned to answer your question in the last few months, so I'm going to give it a go…
Damage, as designed by the Paragon Studios staff, was a rather complex beast pulling from multiple tables with a host of variables, both logical and illogical.
It all starts by determining the base health of a generic entity at a given level. From there, base damage for a generic entity is determined by the formula:
BaseDMG_Generic = (HP_Generic * 0.3) / 3
This is equal to the base damage for temporary powers for each archetype.
From there, the individual archetypes then undergo the formula:
BaseDMG_Class = ((BaseDMG_Generic * (1 - LevelModifier)) + (BaseDMG_Generic * ATModifier * LevelModifier)) * (UnspecializiedLevelEffectiveness/100)
Where:
LevelModifier = 0.20 @ level 1; 1.00 @ level 20+
UnspecializiedLevelEffectiveness = 100 @ 1; 51.93 @ 50
Sounds like a lot? Good thing I already did it for you.
This is then applied to the scale value derived from the RechargeTime and Endurance equations for PVE.
PVP damage undergoes an additional formula:
(CastTime*0.7+RechargeTime*0.04+0.4)*AdjustedATDamageMod*DamageType%*(1/3.25)
AdjustedATDamageMod
Tanker 1.267988141 Scrapper 1.147593307 Blaster 1.229564258 Defender 1.560600789 Controller 1.676678533 Brute 1.352520684 Stalker 1.014390513 Corrupter 1.352520684 Dominator 1.4 Mastermind 1.50901068 Kheldian 1.2 Veat 1.2 Pet 1
Maybe that will help some?