AOD Remastered - Is it meant to be played 100% stealth?

By stealth I mean only takedowns (with the action button approaching from behind).

Aside from The Serpent Rouge, which triggers foes as you activate the music/lighting rig, is it feasible to be stealth at all times?

I'm at the Archeological Dig. I was able to deal stealth with the one near the 2 fuel tanks and with the one in the trailer. I skipped the one from the tent because it seems impossible, so I'm trying the one way bellow.

and I'm having a real hard time in dealing with the guard on the bottom of the dig; he sees everywhere from top to bottom.

I'm able to command the elevator to move and I can go all the way to the bottom from a behind with a hard fall (taking 75% of my HP). I managed to put him to sleep with a dart gun, but still, I would rather do the stealth takedown.