Contradiction with Amos 3:7
While Ezekiel 12:8 speaks of seeing visions, Amos 3:7 states that God reveals his secrets to prophets, seemingly suggesting a more informative than visual communication.
Amos 3:7: Surely the Lord GOD will do nothing, but he revealeth his secret unto his servants the prophets.
Contradiction with Numbers 12:6
Ezekiel 12:8 has God speaking through visions, but Numbers 12:6 shows God communicates with prophets through dreams as well, which may not always be visions.
Numbers 12:6: And he said, Hear now my words: If there be a prophet among you, [I] the LORD will make myself known unto him in a vision, [and] will speak unto him in a dream.