I believe "seers" in that context was meant as people who have and/or do "see" Mary as opposed to "seers" in the scrying/necromancy sense.
That is a nice excuse, but I don't think it will fly. We have been prohibited from communicating with "familiar spirits", i.e., anyone who is dead. Now maybe Mary might be an exception if she were assumed into heaven without dying, but there is nothing in scripture or the early history of the Church to suggest that she did not die like the rest of us.
A lot of what I see in the Mary adoration stuff is superstitious nonsense, which is to be expected if you believe that Mary is running around making appearances all over the world like a spiritual UN ambassador. She is seen on door posts, and trees and clouds and pieces of toast. People come hundreds of miles to view these apparitions, which are no more miracles than Rorschach tests.
I find that all this adoration of Mary and the swooning at so-called appearances of Mary takes away from the focus of our worship, which should be on the Lord and not on his creation. It borders on idol worship. And when you allow things that border on idol worship to go on, you can only expect that some will cross the border. I think people need to ask themselves whether they speak more to Mary than to Jesus, whether they bow more to Mary than to Jesus, whether in their conversations they speak more of Mary than of Jesus. Our focus should be on the Lord and not on his servants, no matter how good they may have been. The Bible states that there is none good but God. So we ought not to attach the name of "Holy" to any person other than God.