It's kindof ridiculous that NZ haven't had to play Bangladesh in tests recently. Bangladesh will thrash the Kiwi's in any format right now (unless McCullum explodes in T20, eg WT20). Bowling is still a big problem for Bangladesh, especially fast bowling, but other than that all their problems stem from not enough test cricket. If the team played more consistently then things like poor catching and dismissals to poor shots would cease to be problems.
The cruel thing about tests is that you can be competitive for 4 days out of 5 and lose and history will forget how hard you competed. Of those 14 losses some were by big margins, but a few were very closely fought, with Bangladesh unfortunately unable to get over the line in any.