Here are some specific questions and answers for the ministries that deacons do. This is partially courtesy of the LiturgyNetwork of the Center for Pastoral Liturgy, Notre Dame University, Indiana.
Deacons in the liturgy:
1. Do they or do they not say "let us proclaim the mystery of faith?"
No. See General Instruction of the Roman Missal 2002 paragraphs 171-186 for details of the ministry of a deacon during the Mass or the Ceremonial of Bishops 155.
2. Should they or should they not receive the gifts "instead" of the priest at the "offertory"?
Either, Ceremonial of Bishops 145: "The deacons or the bishop receives the gifts of the faithful at a convenient place. The bread and wine are brought by the deacons to the altar..."
GIRM 2002, 178, "He also assists the priest in receiving the people's gifts."