that's the thing, if you go with 2 specialist pacers they have to be quality and turn up everyday otherwise you need a 3rd pace option even if they are just a part timer, they need to be at least reasonable though.
the fact is BD are very fortunate to have shakib, a guy who is good enough of a batsman to be in the top 5 and a good enough bowler to basically be the #1 bowler it means BD should be able to take an extra bowling option. so we have shakib and sunny/razzak and 2 specialist pacers. that should be a definate, the final spot can then be decided on pitch, if it's a pacers pitch then take another pacer, if it's a spinners one then go with a spinner.
in one-dayers and t20s we can probably take shakib, sunny and razzak into a match but in tests we can't, razzak has shown he's not a test match bowler. what it comes down to in tests is taking wickets, you have to take 20 wickets to win, so really whoever is the better wicket-taker should be that last spot. a spinner who can't take wickets in test will be just as much of a liability (perhaps more) than a pacer who can't take wickets. why perhaps more? because the opposition will probably score slower against them meaning they'll take longer to get their runs and thus declare leaving less time for BD to chase the runs (even thought that's a really bad way of thinking and i realise this means more chance of drawing but we want to win not draw).
and shahadat is not an option he has a test match strike rate of 71, he is not a wicket-taking bowler, he might take a haul of wickets on occassion but it's balanced out by his overall high strike rate. i'd take a bowler who takes 3 wickets every match over a bowler who takes no wickets for 5 matches then a 5 wicket haul in the next match.
All Time Test XI: 1 Hobbs 2 B.Richards 3 Bradman 4 Pollock 5 V.Richards 6 Sobers 7 Gilchrist 8 Procter 9 Miller 10 Marshall 11 Warne