IPL is hardly the parameter for measuring the true worth of a good cricketer. Look at murali vijay's overall stats and currently valthaty's stats in the IPL. While valthaty is yet to make it his international debut, Vijay has been a failure as a batsman in Odi's. Also the sub continental conditions are similar. Shakib's true worth will be measured in Australia and South Africa. There the fast bowlers will torment him with bouncers and the batsmen will thrash his bowling till no end (actually only 50 overs).
Firstly I did not mention England because they are not amongst the Top 5 ODI teams which are South Africa, India, Sri Lanka, Australia and Pakistan.
In the same series against SA, poor shakib got pwned by steyn scoring 17 of a pathetic 33 and had his bowling thrashed for 67 ending wicketless!!!
2nd ODI: South Africa v Bangladesh at Benoni, Nov 9, 2008 | Cricket Scorecard | ESPN Cricinfo
He must be thanking his stars that the third match was abandoned or else more thrashing was in store.
Same story in the series against Pakistan.
5th ODI: Pakistan v Bangladesh at Karachi, Apr 19, 2008 | Cricket Scorecard | ESPN Cricinfo
1st ODI: Pakistan v Bangladesh at Lahore, Apr 8, 2008 | Cricket Scorecard | ESPN Cricinfo
Consistency against the top 5 teams, while playing away will make shakib a great cricketer. The same goes for players like tamim and imrul kayes. Since Bangladesh prefer only easy games, players like Shakib can never be worthy of top ICC rankings.