Those are not the only Saints in Heaven. There are multitudes of Saints in Heaven.1. Nothing in Revelation 8:3 teaches that those on earth addressed any of their prayers to the 28 (4 living creatures and the 24 elders).
It's not beyond the power of God to make known to Saints things that are beyond human normal abilities. The Biblical examples mentioned in the video are proof of that. Did you see the video?2. Nothing indicates they fully know the hearts from which these prayers sprang forth. Since they do not fully know the hearts of all then they are not the proper recipient of prayer.
1 Kings 8:38-39
whatever prayer...is made by any man...then hear in heaven...for You alone know the hearts of all the sons of men.
Then what do you think is the purpose of the prayers being placed before the Throne of God? Remember that each and every vision in Revelation is what John actually saw. This cannot be dismissed as just metaphor.3. That they ceremoniously present prayers to the Lord doesn't mean they are being spoken to by those on the earth, and then tasked with carrying these prayers to the Lord in order for Him to find out what these prayers are about. The Lord already knows this. To believe otherwise is to deny the omniscience of the Lord.