I have to go along with George here. I do not call the LE, Mark 16:9-20, as it is not part of the original text, based on the two oldest manuscript witnesses we have. That Tatian has it in his Diastessareon means nothing, except it is there and not in the oldest texts available. Tatian may have compiled the LE by looking at the other Gospels of Matt. and Luke, and parts of Acts. I think it is highly likely that the snakebite incident with Paul after the shipwreck is the source of the reference to "taking up serpents". Why not? Speaking in tongues as a requirement or fruit of salvation is taken from the LE. But this is proven false by Paul asking "Do all speak in tongues" in his first letter to the Corinthians. The LE says all will speak in tongues, and Paul denies that. I will take a divinely inspired author like Paul over a cryptic and cultic LE any day. Some sects like the Churches of Christ love the LE because it mentions "belief and baptism" both as requirements for salvation. This is part of the fruit of the LE: baptismal regeneration, while Paul says salvation is by faith, from first to last in Romans 1:16-17.
Going on the the snake-handling now, 100's have died over the years in the American snake handling churches. Some snake handling sects even drink poison based on the LE. Nothing in the teaching of Christ mentions that his followers are to handle serpents. There is an apocalyptic mention of treading on snakes, and scorpions and the power of the enemy (Luke 10:19). So there are four rotten fruits of the LE: the teaching of baptismal regeneration, mandatory tongue speaking as an evidence of salvation, serpent handling, and poison drinking. One could say that these things are merely misunderstandings of a text. but I think not. If the LE is true, then we all need to speak in tongues, be baptized in water to be saved (not because we have been saved), handle serpents, and drink poison.
Do not forget that many early translations of the NT do not include the LE, and that there are alternative endings to Mark. These two facts speak against the inclusion of the LE as the true ending of Mark. These are my 2 1/2 cents. Thanks, Gary