I have a few questions regarding role of MRCP:
Post-cholecystectomy patient with recurrent pain (stricture?)
Hilar masses causing compression of the biliary system
Query for ductal stones ( i think MDCT should be done here)
Lastly, role of imaging (any form) in cholangitis, what benefit would it be in suspected cases? would it alter treatment.

Well, for post-cholecystectomy (? Stricture), how about going for MRCP that will also show any residual CBD stones. For hilar masses causing compression of biliary system, may be a thin slice CT would do. However, I can’t quite understand how CT is preferable to MRCP for ductal stones!!
Regarding cholangitis, it is a clinical diagnosis (obst jaundice, RUQ pain and fever) that requires antibiotics regardless. Here, I think ERCP is both diagnostic and therapeutic. Same goes for PTC probably after a failed ERCP where drainage of an obstructed system is required.