+1 for being a connoiseur on one of the best games/series ever published
I've never mastered ghosting, but I did manage to go through a few missions without KOing anyone. Never on a first run, though, except for that mission on Thief 2 where it was a required objective because you had to frame someone, and you could leave no evidence of ever being there.
As for DDO, sometimes the way it's designed keeps the player from any approach that's not "full heads on" - e.g., the fights where you lock the player in a room and spawn the mobs/boss. There's not much variety of strategies for a situation like this.