I'm in agreement, I wish it was harder. I would prefer both the player and the enemies to be far more vulnerable on Authentic difficulty. If I shoot an enemy in the face with a sniper round I expect them to die, not 50% of the time just pop back up and return fire, it's artificially raising the difficulty making the enemies take multiple hits (sometimes I hit an enemy four times with rifle rounds before they go down). I would prefer it if an enemy who isn't hit in a vital organ goes down injured.
What I miss from Sniper Elite 3 on the toughest difficulty is having only one life to complete the mission, die and that's it. It added a great level of tenseness to gameplay.
I would love for Authentic difficulty to be a high benchmark for difficulty in the gaming world. There are plenty of other lower difficulties to suit people of all skill levels so I think the devs should go all out to make Authentic REALLY tough i.e. as authentic as possible. Maybe things like one rifle round removes all but the tiniest amount of health (nobody likes to be one-shot killed), two hits kill you. The snipers maybe SHOULD kill you with one shot because there's the audible warnings that tell you when there's a sniper looking in your direction AND when they've spotted you. Personally I'd like these audible warnings removed as they just make the game easier.
Maybe restrict the number of medkits/bandages you can carry as well.