“The Maggid Shiur you mentioned who lambasts Daas Torah based on his Rebbi’s final decision (and who quotes his Rebbe reverently about all types of non-Torah topics), also holds that when it comes to the 13 principles there is a Psak, for some reason”
Obviously there are people today who say that there is a psak. He quotes his Rebbe reverently but that doesn’t mean that he agrees wih him on everything (although that is really more relevant to the Daas Torah thread). Also, for the record, I have never heard him say that there is a psak (and I’ve listened to a bunch of his shiurim). Do you have a specific place where he says this, or are you just assuming?