Hi Brian,
You asked, "Is that the only verse in all of scripture that supports your claim?"
No, it is not. However, it is the most explicit exposition, in Scripture, of saints in heaven offering the prayers of saints on earth before the throne of the Lamb, and so it is the best "proof text" I have to give. It's simple, straightforward, and explicit.
You wrote, "Is it good to take a book like Revelations, which is almost poetic in its launguage, and use it as a proof of a belief?"
Of course it is. Irregardless of the particular genre of Scripture, St. Paul tells us in 2 Tim 3:16, "All scripture is inspired by God and is useful for teaching, for refutation, for correction, and for training in righteousness, so that one who belongs to God may be competent, equipped for every good work."
St. John, in his Apocalypsis, shows us the Heavenly liturgy. This is why he says that he was taken up "on the Lord's Day". The first Christians referred to Sunday as "the Lord's Day" and it was on that day that they gathered and celebrated the liturgy of the Word and the liturgy of the Eucharist. The entire book of Revelation is liturgical from start to finish, and John's vision reveals the heavenly worship in which we partake in when we partake in the earthly liturgy.
John shows us that Saints in Heaven offer the prayers of the saints on Earth before the throne of the Lamb. You can attempt to demolish the article "the communion of the saints" from the Early Church creeds by interpreting this verse in such a way that it no longer speaks for itself. But, I'm not you. I'm a member of the one, holy, catholic, and apostolic Church, and I hold to the faith that comes to us from the apostles, the faith that comes from Scripture interpreted rightly, the faith guarded by the martyrs, and the faith as practiced in the Christian Liturgy from the time the Apostles celebrated the Passover Seder meal with our Lord in the Upper Room.
The first heretics to have a problem with the article of the creeds concerning the communion of the saints came along only 5 centuries ago. For 15 centuries, we don't have a Christian arguing against asking St. so-and-so in Heaven to pray for us. For a Lord that promised the gates of hell wouldn't prevail against His Church, He did a pretty poor job for a good millenium and a half.