This is why stats are not the end-all-be-all : Saqlain has a lot more lower order wickets because when on song,he was better at beating the bat than Murali and Warne and thus could bowl prolificly in the death. So obviously he will have more lower order wickets if he doesnt just pack up by the 40th over.
Saqlain is no mystery- i've explained several times that Saqlain just 'lost it'.
Spinners tend to just croak and die all of a sudden - just like how Qadir, Bedi,Chandra, Prasanna,Laker etc. just ground to a halt all of a sudden. Plus Saqlain massively overused the doosra after he reinvented it to the point where his regular offbreak bowling began to suffer badly. Basically, he went from being a really good spinner to a spinner with a stupidly successful mystery ball who became overly reliant and one dimentional due to the stupid amount of success he got with his mystery ball. So by the time good batsmen finally figured out his mystery ball, he'd regressed significantly in all other skills. As a result, he went from boom to bust. His downfall was further compounded by the fact that Saqqi was never an extraordinary turner of the ball ala Murali/Warne. But before he began overusing the doosra, his loop and flight were far far superior to Warne's and shades even Murali today when on song. But he then got caught up in the whole 'he who turns more is the man' contest and started bowling totally flat. In the last test in Multan, he was bowling super flat and just trying to get as much spin as possible despite the fact that he'd have been better served by loop and flight on that pitch.
This is like what happened with Agarkar too, though at a much lesser extent : he came in rapidly, got figured out and was bust soon.