Observing team composition worldwide in terms of fast bowlers, I have come to this conclusion. We need a pool of three types of fast bowler and/or fast-medium (only over 135kmph needs apply!)
1. Main strike bowler: He needs to carry out the main assult and inject a psychological edge over opposition team. With few exceptions, he should have genuine raw pace (or at least young enough to work on his pace) with pixel perfect line-length. He should be experienced and intelligent enough to adjust his length in different parts of the world. In case of BD, Masrafee fits exactly in the position (high hopes for continuous improvement). The down side is that we don't see anyone like him coming through the pipeline yet. Overseas examples are Shoaib Akhter, Imran Khan, Wasim Akram/Wakar Yunis (Pak), Alan Donald (SA), Richard Hadlee (NZ), Danis Lilly, Craig McDormot (Aus), Chaminda Vas (SL), Javagal Srinath (Ind), Malcom Marshal, Curtley Ambross( WI) and some English quicks once in a while.
2. And his striking partner: He needs to complement the main bower in every possible way. Line and length is as essential as pace and he should also keep things tidy at the other end when he and the main bowler are operating simultaneously. On the occasion of below par performance from the main bowler, he should have the ability to rise to the occasion and cause severe damage. In the case of BD, Talha (long term prospect, once he gets his act together i.e. fitness and stops spraying the ball all over the pitch but hopefully experience will amend those), Tapash (short term, we all know about him and he can be used as work-horse later) and Shahadat (future prospect, he needs to be well groomed for the position and the rapid improvement necessary. He's tall so he can extract bounce with pace which Masrafee might lack and complement him well). International example include Steve Harmison (Eng), Jeff Thomson, Jeson Gilespie (Aus), Wasim/Wakar, Moh. Sami (Pak), Courtney Walsh( WI), De Villiers, Ntini (SA) etc.
3.The Work-horse: He needs to keep things tidy as a change bowler and work for a set goal. Most likely bowling in tandem with slow bowlers (spinners), he should be able to produce odd moments of sheer brilliance. Generally a cool customer 'cause he doesn't give away too many runs. In Musfiqur Rahman, the BD team already has a real work-horse. He's a good bat too. Tapash could be used as a work-horse, if rapid development of some young talented players permit him to be, or the in case of Mushfiq's injury or bad patch. Successful foreign example in this category would be Mathew Hoggard (Eng), Shabbir Ahmed, Akib Javed (Pak), Jack Kallis (SA), Brett Lee (Aus), Ian Bishop, Joel Garner (WI) Chris Cairns(NZ)
The aforementioned categories are actually a generalised idea. A few exceptions do exist in world cricket. The likes of Glenn McGrath(Aus), Shaun Pollock (SA) etc have work-horse like attributes but they are in many ways the main strike bowler for their respective teams. And India always made Javagal Srinath look like a work-horse for valid reasons!