Swann gets good drift, but he has a naturally high release point, which is going to reduce it to some extent in comparison to Hauritz.
Hauritz bowls with a lower arm, so the ball curves outwards on with the arm, and he does get quite a bit of drift. Swann doesn't get as much in total, but he has a better combination of drift and dip (which Hauritz doesn't get a huge amount of), and when he gets it right Swann's drift occurs later, whereas Hauritz's is almost out of the hand.
Harbhajan doesn't really get a huge amount of drift, because he's almost past the perpendicular (which you often need to be to bowl a doosra). He angles the ball intowards the batsman at times; Ponting spoke of how they were trying to help Hauritz develop a similar tactic for India (which was complete madness, as they are such different bowlers). When Harbhajan gets this right, and manages this whilst still spinning into off stump and the batsman can't work him to leg, it's super hard to play, especially in sub-continent conditions.
