No i'm fully against quick time events, what i would suggest is that they take better cover, move around a lot more so even if you are approaching stealthily you have a harder time of both finding your target and taking them out. Maybe they have stronger armour like the heavys helmets but maybe take a couple more shots to get off.
At the end of the day I do like realism (one shot head kills) but its a game and you have to draw the line between realism and what makes killing a supposedly stronger enemy a more enjoyable accomplishment. I killed them and it didn't feel like an accomplishment when it should have.
As always just my opinion and feel free to disagree.