Avi K. The Tzitz Eliezer was a prolific posek who obviously researched his subject exhaustively before issuing a psak. But that is called being a posek. Any Rov who doesn’t know everything about a subject will refrain from paskening on it. A few years ago, I had occasion to ask a world famous Rov and Posek about a certain subject. He said to me, Ich bin an am ho’oretz in dem inyan. (I am ignorant in that subject). It is quite a specialist area of halocho. He sent me to another Rov who was well versed in that area.
This is the point where the Godol Hador question begins. Who is the final address where all difficult questions end up?