When I play as medic, I almost never get killed. Heck, if you see my stats, I once lived for an entire hour as Medic on 2fort with many ubers with that as well.
However, with every other class, I play super aggressive, and since I play a lot (looking at HLX, I have one of the longest times playing), I get killed a lot, but my kpd is pretty decent, I think.