what im going to say will sound harsh as well. 3 sumatran tigers are obviously better than 2, but with, as Toria pointed out 2 cubs left to represent the new bloodline of Binja so the loss of this cub isnt sooooooooo bad.
from the point of view of housing the cubs in the future, it just got a bit easier, and may just help to speed up the process of integrating the new Australia Zoo cubs into the breeding program by creating a new (or potential) space.
this is the second litter of cubs born recently, the other being Tarongas, to suffer from certain defects early on in life. whether this is a manifestation of inbreeding is debatable, but certainly the 3 new Indonesian cubs and the infusion of new genes they bring are a huge asset for this program.