What is the point of Mark 13?

Mark 13 caused me some considerable vexation when we reached it in Christianity Explored. I find it difficult because much of it seems to point toward the passion narrative, some seems to fit better with the early church (pre 70AD?), but some of it doesn't seem to have happened at all. However, this is perhaps only a problem if we assume that Jesus is giving a straight answer to the disciples' question ('when will these things be, and what will be the sign when all these things are about to be accomplished?') which would be most unlike him. I decided to see what the explicit commands that Jesus gives were to get more of a handle on the passage. They are:

• 'See that no one leads you astray' (v.5)
• 'do not be alarmed' (v.7)
• 'be on your guard' (v.9)
• 'do not be anxious' when before governors and kings about 'what you are to say' (v.11)
• 'Pray that it may not happen in winter' (v.18)
• 'if anyone says to you, "Look, here is the Christ!" or "Look, there he is!" do not believe it' (v.21)
• 'be on guard' (v.23)
• 'know that he is near' (v.29)
• 'Be on guard, keep awake' (v.33)
• 'stay awake' (v.35)
• 'Stay awake' (v.37)

Jesus is not concerned that we know when the end will come because no-one but the Father knows that (v.32). In that respect he doesn't answer the disciples' question. Instead he is concerned that we are aware that the day could come at any moment, but that nevertheless we shouldn't panic when signs of this appear.

Perhaps Tom Torrance is right when he comments on Mark 13:

He has told us that [his second coming] will be sudden, and just when we expect it least, like a thief in the night. But there are signs of His coming. They are not signs that tell us when He will come, but signs and pledges telling us unmistakably that the end will come, as surely as day follows night, and that world-history will be brought to a close [...]

God gives us signs in history like that, not in order to predict the time of Christ's coming but to keep us faithful to our task of preaching the Gospel to all nations, and serving of our fellow-men in acts of unstinting love.

(pp. 21-22, When Christ Comes and Comes Again)

I'm still not sure, but I'm still thinking.