No.
1) healing is primarily done by healers, you are simply making sure your HP is at a level to surivive. That's part of the surival, not mitigation.
Mitigation is what you do to reduce damage. You can have as much HP as you can, but if the hit exceeds taht hp you need to reduce the hit.
2) Self healing from NF is classified as sustain. Its useful to use if you know you will live from a tankbuster with cooldowns, then go ahead and use NF to help self heal/sustain after the hit.