MPA mission area is, in the year 2016, no longer only sub hunting. Won't comment on how much most of the press still don't know about ASW, but it isn't getting any easier. The improvements in AIP tech will see to that, particularly for any nation whose submarines are not required to support power projection. As a sea lane or area sea denial asset, a diesel sub is quite good, and one with AIP is even better ... and most importantly, for many small to mid sized nations, affordable.