It seems to me by your posts that you agree with us that there is only one mediator between God the Father and us, through His Son, our Lord Jesus Christ. While the Roman Catholic Church has acknowledge that Mary participates in dispensing grace, it has not been formally approved that Mary dispenses all grace.
Given the fact that you seem to believe there is only one mediator through our Lord Jesus, if the Church were to declare Mary to be co-equal in dispensing God’s grace, would you denounce the Church’s heretical views?
Excellent question.
Alex did say, though, he thinks Mary is a mediator per John 2:3
http://www.freerepublic.com/focus/religion/2451801/posts?page=167#167
That would be heretical if Mary were proclaimed the source of grace. That we find Christ through Mary, and therefore receive all of His grace through Mary is in itself not heretical; it is a view held by many in the Church. Ad Iesum per Mariam, we often say.
My personal opinion is that, for sure, one outward sign of election is robust Marian devotion. On the other hand, the venom with which Marian devotions are met is a sure sign of a soul in great danger. I don't know if that i strue in absolutely every case, dogmatically, but this is a rule of thumb I have.