Is it essential to know what the original readers thought?
Not essential, because we can't know for sure, but without seeking to understand the author's original intended meaning, we end up imposing our own thoughts onto the text -- and, as I responded to Dick Johnson, we turn a Bible study into a self-study. In addition, our hypotheses about the author's original, intended meanings provides some parameters around what interpretations are acceptable or not in the present day.
To return to Mark 16:1-8, I do not think that Mark's intentions were to deny the reality of the resurrection. Thus, an interpretation that does so, has strayed too far from the historical meaning of the text. I think that it is Mark's intention to show how the disciples failed Jesus. One can compare Mark's comments about the disciples with Matthew's. In Mark 4:40 they are people of "no faith". The parallel in Matthew 8:26 they are described as having "little faith". In Mark, the women say nothing. In Matthew, they tell the disciples. When read as a whole, I agree with Powell's statement about Mark's gospel:
Jesus keeps his disciples in spite of their complete faithlessness to him (Mark 14:26-27; 16:7). This is surely the most important point all. Jesus never rejects any of his followers, no matter how inadequate they turn out to be. Even when they desert him, deny him, and leave him to die, even then the message that goes out from the tomb on Easter orning is, in effect, "go, tell Peter and the others that I will be weaiting for them in Galilee -- I intend to see them there." This is frankly incredible! Why doesn't Jesus rise from the dead angry? Why wasn't ditching him in his hour of need "the last straw"? We might have expected him to fire the whole lot and find twelve new disicples who would prove somewhat worthy of him. (Loving Jesus, pp. 105-6)
I think that's a message that Mark intended his original audience to grasp -- or that they are grasped by this message as they hear and enter into the whole story of Jesus and his disciples throughout the book of Mark. The depth of this message is lost or at least watered down when one starts impossing Matthew and Luke's stories into Mark, such as understanding the women not as utter failures at the end. I don't think that Mark intended his audience to think that women eventually succeeded -- and we shouldn't think so either -- at least when studying Mark.