If anything the show has done a pretty good job of showing how tough it is to kill someone iirc. Snow took multiple hits to the stomach then final dagger to the heart. Stannis was wounded and alive for a while after the battle. The Hound survived not to mention his big bro. Beric keeps coming back to life. Robert Baratheon took a while to croak after being gored by a boar. The only easy deaths seem to come in big fights and to people who don't mean shit to the story or to more prominent characters when hearts and are stabbed, throats cut, or heads lopped off.
Obviously I don't remember every single death/murder scene, but that's just what stood out to me.