If my sister-in-law says she is asking both her patron saint and me to pray for her, how is it one of us prays while the other mediates? We're either both praying for her or we're both mediating for her. As I said before, Catholics ask both the living and those who have passed on to pray with us.
By your definition each time a Catholic asks someone for prayers we are asking for mediation. We're not, but that is how you say you see it, and you are quite definite about it. My sister-in-law and I needed a good laugh. So thank you. We're thinking of adding "Mediator" to our next resume. Gales of laughter.
The point: Mediation never comes up when Catholics ask people (both the living and those who have passed on). It was you who walked in and claimed that what Catholics "really" do.