Like a lot of other people said here, there are no other options. Sakib is overloaded with work. We do not have too many options here. Mahmudullah is still unstable with his position in the team. Don't even say Mash, he is not a regular. So no other options.
The thing we need to learn is how to use our bowlers. A guy like Rubel should never be used as a death bowler if there is a set batsman on the other end. Rubel is more of an opener material. You can have him hit the deck hard with pace and then bring in the spinners later. That is his role. Once the ball gets old, he is of no use in an ODI. Its all about knowing your own players as a captain. That is the only way to utelise them right. If you don't know which chess piece moves in what way, you can not be the king. You might as well be the pawn in the game.
But having said all of this, I have to say that in the end Mushy went for the Win!! He did not want to settle and see where it goes which is why he made that change. He thought a fast bowler would be more threatening. Bad mistake with that move, but at least he had the right attitude. A sharp contrast from any BD captain before Sakib. At least you know he believes in his team!
"...cometh the hour; cometh the man (Sakib)"