I was raiding a base earlier today (trophy hunting, not farming), and sent my heroes in for some cleanup. Queen went straight for the TH like she was supposed to, King gets a little sidetracked. King activates skeleton trap before dying, AQ leaves the Town Hall ONE HIT BEFORE DESTROYING IT to go kill the little guys, runs into some other defenses... and dies... and I lost.
So I agree they're a very frustrating thing, and I'd have preferred they never existed, but that's the way it is and we have to adapt as best we can. CC troops do the same thing too unfortunately, albeit more predictably since you see the CC beforehand. Troop AIs have never been... umm... ideal, and probably never will be.