An oft discussed optimization trick in the 4th edition era was the use of Nusemnee's Atonement on a Dragonborn Dragon Magic Sorcerer in order to recharge your breath weapon with the use of the Ancient Soul feat. Ancient Soul reads as follows:
Your dragon breath power is considered an arcane attack power. In addition, if your dragon breath power deals damage of the same type as your Dragon Magic class feature gives you resistance to, you gain the following benefit: Whenever you take damage of the type dealt by your dragon breath (after the damage dealt is reduced by your resistance), you regain the use of your dragon breath if you have already expended it in this encounter.
Dragon Magic Sorcerers get the following feature:
Choose a damage type: acid, cold, fire, lightning, poison, or thunder. You gain resist 5 to that damage type. The resistance increases to 10 at 11th level and 15 at 21st level. Your arcane powers ignore any target's resistance to that damage type up to the value of your resistance.
Lastly, Nusemnee's Atonement reads as follows:
Whenever an attack you make would damage an ally, you can choose to take the damage instead. You have resist 5 against damage taken this way. You can choose to take the damage even when you are dominated. This resistance increases to 10 at 11th level and 15 at 21st level.
My question is: Since Dragon Breath is an Arcane Power because of Ancient Soul, do you ignore the specified amount of your own damage resistance, even though the feat says "after the damage dealt is reduced by your resistance"?
Normally a Dragon Magic sorcerer ignores resistance up to their own damage resistance from the class feature, and the fact that this trick was so heavily discussed on forums makes me wonder how it worked in practice when, if you were ignoring your own damage resistance and only gaining the 5 /10/15 from Nusemnee's Atonement, you would be dealing a considerable amount of damage to yourself and run out of hit points very quickly.