Christians? Christian means one follows the teaching of Christ and His apostles. Would you please show where they taught the assumption of Mary and the requirement to believe that to be part of His "church"?
Would you please show where Christ and His Apostles taught "the Bible alone as the sole or ultimate rule of faith?"
This principle cuts both ways, if you want to be intellectually honest.
Luther's tradition doesn't show up until 14 centuries after Christ.
The Assumption can be traced back at least to the fifth century in writing. Additionally, there are no relics of Mary, which would have been prized possessions in the early Church.
There is also biblical evidence supporting Mary's Assumption.
We know from Luke that Jesus has inherited the throne of David, and from Revelation that he holds the "key of David." Jesus is the King of the eternal, redeemed Davidic Kingdom, the Kingdom of God, or Christ's Church.
In the ancient Davidic kingdom, the mother of the king, the "Gebirah" or "Queen Mother" held a position greater than that of the wives of the king. The Bible records her sitting on a throne at the right hand of the king.
Mary, as Jesus' mother, is the Queen Mother of the eternal, redeemed Davidic kingdom. She is the Queen of Heaven, as seen in Revelation.