Scaly piscine
Cricket Web: All-Time Legend
Really. In 2014 the only team they beat in ODIs was Zimbabwe. They lost the other 12 ODIs.Not true. In the last 5-6 years, they have beaten New Zealand and West Indies along with making the final of the Asia Cup 2012. 2015 was not the only year and it was certainly not just a purple patch. You're just not familiar with Bangladesh cricket.
In 2013 yes they won a series against a comical NZ side which had McCullum as their sole 'spinner' (seriously) with some occasional part-time backup from Devcich and Kane. But then again they also lost a series to Zimbabwe.
In 2012 they had a decent year, all home ODIs winning 5 out of 9. Although 5 of those ODIs were against a West Indies side boasting a middle order with the likes of Devon Thomas, Pollard, Sammy and Dwayne Smith.
In 2011 they managed to beat England and West Indies. So that was 2 wins out of 13 ODIs against proper sides. They also beat Ireland and Netherlands. They lost a 5 match series to Zimbabwe.
In 2015 they won 13 out of 18 matches (one each against Afghanistan and Ireland, while 3 were against Zimbabwe, but as we've seen they lose a lot to them)
So yes 2015 was a purple patch. This year they've had two tight matches against Afghanistan and lost one of them. They're favourites to win this one comfortably. But they're not a good ODI side and they play the vast majority of their ODIs at home or in Zimbabwe.