Is intermittent, intense pain that radiates down to my labia normal 6 months post incisional hernia repair in the groin area?

No: I would be worrying about a pudendal nerve injury from the hernia surgery. A peripheral neuromuscular type neurologist should work this up. A medication such as Neurontin (gabapentin) may help prevent or alleviate this lancinating pain.

Local anesthetic: Unfortunately nerves can be damaged in surgery, especially when it's the second operation (you said "incisional hernia"). Your surgeon shoudl be able to inject local anesthetic into the area near the incision to see if this is really a nerve, or just scar tissue. See the doctor who operated on you.