You don't need more low quality numbers and testing. What is really needed is a little more theory on heat transfer, fluid mechanics, and flow through pipes and fittings. That will give you some perspective on "the big picture"; there is no way to fully optimize flow and water velocity in every person's setup with a waterblock (or radiator, fitting, pump, etc) roundup. It is just too complicated a problem. However, to some extent the numbers are there if one looks at them in Joe's waterblock roundup. For the most part, flow rates of 0.5-1 GPM are typical with ~200GPH rated pumps and 3/8" setups. For 1/2" setups and the same pumps then 1-1.5GPM is more normal. Look at Joe's temperature vs. flow data and for each block you can get a reasonable idea as to how it will handle lower or higher flow rates. You can also see for most of the blocks that there is a 1-3C improvement in the range of 0.5 to 1.5 GPM.
Here is some old data of mine when I first got a flowmeter. This data doesn't have the proper resolution (I am nearly ready to start testing blocks now though with much better temp resolution and decent water temperatures finally), but it shows the general trend:
Comparing the block vs water temp would be better, but since the pump puts more heat in at lower flow rates (it was throttled with a ball valve) then this graph might perhaps give a better estimate of "overall system performance". I personally am more interested in block performance only at the moment...