I have noticed if you play fight the final boss a second (Corypheus) time with a character you can receive not 1 but all 3 class armour. I knew from previous testing if you go back to the previous floor after fighting Corypheus you could not activate a Power Nexus if you followed Janeka. However you can still interact with a Power Nexus and rotate columns if you followed Larius.
However I did not know that when my mage (second true character), following a complete disaster fighting the 3 golems and destined to betray Larius in order to avoid fighting 3 golems which can kill a archdemon. Playing the mage from my last save where I could pick party members to get the Family Outing achievement (second run) I actually got all 3 class armour. At the time I assumed you could not go back interact with anything. Now after spending (rather wasting) several hours and more then 200 "saves" mostly area transistions, from noted last save, I must admit defeat.
I actually despise how mages are in DA2 since they are designed in such a way the simplicity of using a sword and shield is too confusing for mages (and rogues) to understand. Not only are they too retarded to use a sword and shield, but if you want to access the mage sets you have to "waste" points just to put on clothes. I design characters based on the warrior from DA1 so you can see the problem. My mage uses the "spear" of Parthalan or "combat" staff Malcolms Honour and body armour Cuirass of the Centurion and I would like equip my mage with the warrior warden armour. Note the terms I use for the weapons and it will explain the armour I listed.
With everything said, the double digit billion dollar question I have to ask is this. Has anyone ever "arranged" the game (without cheating) to give you all 3 class armour if you miss you first opportunity?