P-8A , SH-60B , P-3C , Su-34 – anti submarines warfare

from what i understand there are several method for aircraft to detect a submarines :
1) Radar = only work if the submarines surface => useless if submarines try to hide
2) IR = only work if the submarines surface => useless if submarines try to hide

3) magnetic anomaly detector (MAD) = only work if the aircraft fly at low altitude and , past the exact locations of the submarines => pretty useless , i cant understand how they can even find the submarines with this method

4) drop Sonobuoy = basically mini sonar , personally i think this is the most practical method because it allow aircraft to detect a submerge submarines without fly over head of it however i doubt the effectiveness of it , if submarines are so quiet they can hide from big sophisticated sonar on destroyers , aircraft carriers and other submarines wouldn’t that mean tiny sonar on Sonobuoy will be quite useless ?

due to reason above i wonder how effective are these aircraft such as P-8A , SH-60B , P-3C , Su-34 in search and destroy submarines ? ,if it just to deliver torpedo wouldn’t it be much better to use ASROC ? http://en.wikipedia.org/wiki/RUM-139_VL-ASROC