http://www.catholiceternaltruth.com/2010/08/assumption-of-mary.html might address your point to your satisfaction.
Just WAY too much ASSUMIN' going on!
In Romans 5:12[4] it is explicitly stated in Scripture that death is the consequence of sin. This is not an isolated passage in Scripture St. Paul reaffirms this over and over again in his letters.[5] The Holy Scripture attests that sin and death came from Satan and for Mary to be in complete enmity of Satan she must necessarily be free from sin[6]