Personally, I wonder if the scenario of some kind of aircraft damage (say, caused by an O2 bottle fire) that affected the flying characteristics of the aircraft, without it a being a major impediment, was considered in the flight path projections?
This would have the effect of shortening the calculated total flight distance - and this figure appears to me to be the singular major "rubbery" factor that has impacted on the success of the search.
If the total flight distance was say, 10% less than the "best projection", this obviously puts the aircraft well North of the designated search area - and the MH370 debris finds around Mauritius most certainly point to a more Northerly crash location.