When does Special Duty trump life threatening disability?

I have recently been dealing with the VA on my disability. I really started pushing for an increase on my percentage when a fellow soldier that I served with left the military. We started talking and I found out that he was released and was given at 70% disability rating. Now knowing that my good friend was in an Airborne unit for sometime his rating was for his knees and one elbow. Now this condition hasn't stopped him from working or anything of that nature.

So that really got my gears turning. Was his rating increased because of the special duty that he was apart of? Now I have a life threatening condition that I have been dealing with for 11 years. I am a walking time bomb and I could throw a blood clot and it could kill me, but I was given a rating of 10%. I filed a claim and in the end, VA told me that my leg practically needed to be falling off and I had to have no use of the leg to be considered for an increase to 40%.

I just found this interesting. To add to this another fellow solider who was also eventually in an Airborne unit was discharged for the same issues and landed him at 70%. These two only had two years extra in.

Let me hear your thoughts.