This site has a breakdown of casualties by what they did. 11Bs did take a real pounding, but interestingly, the tankers, 11Es, were the ones who had it the worst, with a 27 percent KIA rate.

It looks like out of the 58,169 deaths the US had in Vietnam, 47,434 were battle deaths. Also, 35,296 were just infantry and Marines (although that would include disease and accidents). Another 3k were Helicopter crews. The biggest hiccup in the data is that it doesn't give us the total number deployed, BUT, it we take a representative year, in 1969, of the 440,029 in Vietnam, only an estimated 67,600 were combat arms, or 15 percent (Most of the numbers are sourced from the National Archives, but I'm trusting his estimate for the math here).

Now, according to the VA, 3,403,000 people deployed to Southeast Asia during the whole involvement we had there, 1964-1975. That gives the total casualty rate was 2 percent of everyone who set foot in the region. If we assume the 15 percent holds true, that's 510,450 combat troops who cycled through the area during the whole time the US was there. So while they only made up 15 percent of the total US presence there, they would have a death rate of 7 percent, or almost three times the overall rate (Note that that is a super rough estimate as the 35k deaths is just infantry and marines, while the combat arms total would include other combat roles. If I was using just the 11X and Marine 03s for total deployed, that number would be even higher).

Support personnel would be a very tiny 0.7 percent death rate (and again, that is high since I don't have a total breakdown of deaths by MOS, so some deaths which were in fact combat arms are not included in the 35k number I'm using).

So the TL;DR here is that someone who was out there, carrying a gun in the jungle had at least ten times as likely a chance of being killed as a paper pusher.

Approximate numbers for all deaths, not just KIA:

Total Casualty Rate for Southeast Asia = 2 percent

Total Casualty Rate for Combat Arms in Southeast Asia = 7 percent

Total Casualty Rate for Southeast Asia for support personnel = 0.7 percent

One last addendum. The US included people deployed to Southeast Asia in general, so many of those support personnel might never have set foot in 'Nam, and been in Thailand instead the whole time, and the flipside is that people considered support personnel might have ended up in combat... and some 11Bs might never have seen the elephant.

The US deployed a total of ~536 000 combat troops to Vietnam, the total number of casualties were ~58 000 giving us a casualty rate of 10,8%. There were however over 300 000 wounded.

If we look at single year we get a better picture of what individual years were like. -68 was the high point of US involvment in Vietnam with ~389 000 combat troops deployed, during this year a total of 16 592 were reported (highest individual year in the war) for a casualty rate of ~4,3%.