Tony,
I guess the model for thinking about directions of time is of lightcones. The broad spectrum of potential input into any event, vs. the broad spectrum of effects any event might have.
While I get alot of grief for making this argument, I think time and temperature are two sides of the same coin, similar to frequency and amplitude. So if you were considering ways to judge potential input and output of any event, as a scalar might be a more useful concept, rather than a vector. When you try to follow every possible thread of energy transfer, the computational complexities quickly go off the scale, as not only are there lots of potential direct threads, but interactions between these various vectors. Yet when we look at it as a scalar, it is more about overall input.
One thing to keep in mind is that sequence is not inherently causal. Yesterday doesn't cause today, anymore than one rung on a ladder causes the next. What is causal is energy transfer. Me tapping on these keys requires some form of energy transfer for the words to appear on the screen. The sun shining on a rotating planet is the sources of energy which create the sequence of events called days. So if you are trying to use a vector of sequential events to model causal factors, you go off track. The causal process can be modeled in terms of scalars; temperature, pressure, weight, speed. Think of cumulative human activity, vs. individual activity much as a pot of water, vs. one of the molecules of water in that pot. The motion of that molecule is constantly being affected, both adding and losing energy as it bounces around the others. So when you think of it in terms of the lightcone of input and output, it is more of a scalar, of all the combined factors going into it and proceeding from it. Which is not to say there are not many vectors of direct energy transfer, but that they need to be keep in context with all the cumulative and non-linear transfers. Much as economic statistics are a measure of the cumulative human activity of lots of people traveling their particular vectors.
The point being, not so much what is happening, but how do we mentally process it. I think the left, linear side of the brain is a form of clock, the vector of time, counting out sequence, while the right, intuitive side is more of a scale, weighing all the possibilities and seeing what emerges/rises to the top.