The theory sounds good, but I think it important to test ideas before believing them. One way of testing your hypothesis—that it is really hard to over-ride the immediate discomfort of an unpleasant decision—is to look at whether aversions of comparable or greater magnitude are hard to override. I think the answer in general is 'no.' Consider going swimming and having to overcome the pain of entering water colder than surrounding. This pain, less momentary than the one in question and (more or less) equally discounted, doesn't produce problematic hesitation.

One answer I'd anticipate is that the procrastination effect (for work but not swimming) is "nearly impossible to get your brain to remember." But what about the fact that when we do remember, it doesn't solve the problem. (If it solves yours, I'll concede this point.)

Another way of testing your hypothesis is to determine how adaptive or unadaptive if, as you suggest, the bare fact of making a decision is inherently very difficult. Much of the adaptive advantage of thought is insulating the organism from the effects of carrying out the act, including, one should think, from the emotional effects. An adaptive design would compensate for any hyperbolic discounting by making the decision much less aversive or, why not, even pleasurable—which is my experience of the deciding process.

A different explanation for procrastination—one which can help overcome it—is that when we procrastinate we're self-deceived about our preparedness for the task; we inarticulately perceive that doing the tasks out of order would harm the product. The solution, obviously, would then be to figure out what preparatory work you're neglecting and do it instead. I only claim validity for procrastination in writing: there's something to be said for starting small. Here's my series in defense, "On the irreversibility of writing: Procrastination and writer's block—Part 1. Premature composition limits thought and weakens style." It's in three parts, starting here: http://tinyurl.com/37skhks