When the work "dried up", I noticed the percentage completion for the project was 20% and figured perhaps some landmark had been reached possibly explaining the lack of new work. since then, the percentage completion has dropped incrementaly down. Today, it says 17%.

The percentage complete going down, is a result of the equation WCG are using to calculate time remaining. As has been noted elsewhere (CEP2 & OET as two examples), as the calculation takes into consideration the number of WU's completed in a certain timescale, it can have dramatic consequences on the estimated remaining length of the project.

It has been suggested (but not taken up), that the calculation should be changed, so that it takes into consideration the total number of WU's done and the over all total for the entire project (or, if that's not known/available, the approximate length of the project - i.e., when we're 6 mths into a 2 yrs project, it's 25% done).

Unfair? - not really. Like anything else that is scarce in this world you have to work harder to attain. I set myself a target of 2 years for this project - and succeeded. Had I just enabled the project - would have failed. When things are in short supply it takes effort, research and awareness together with time commitment to be ahead of the pack... Analysing posts on the forums and acting on the information gained paid off for me...

based on your avg runtime per day you should focus first on OpenZika project to get sapphire (2y) before end (03/2017)

By the luck of the draw I finally got one after about a couple week hiatus. It was a big one too, 38 hours.
Cheers