I'm not nullifying the miracles in the great tribulation for I believe this will occur, but what I'm saying is specifically, the Lord is speaking to His disciples in that passage telling of things that would happen shortly. The signs would cease with the Apostles and Israel's rejection of their Messiah. Once they are cut off, the Gentiles require no signs, but live by faith.
This is where we differ. I see everything Christ said applying to everyone who believes His Word.
John 14:12 Verily, verily, I say unto you, He that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father.