Slic3r 1.1.6 has a setting "Seam position" under "Print Settings > "Layers and Perimeters". Try changing that from the default "aligned" setting. It won't get rid of the blobs but they should not then all be in the same place - which may or may not be an improvement. There is also the "Wipe while retracting" option under "Printer Settings" > "Extruder". Checking that may improve things (but be aware that that setting caused problems with older firmware). You may also find that unchecking the box "Retract on layer change" may improve things by decreasing the time between the Z height change and the start of the next layer printing, but I have not experimented and it could make it worse instead.
I have a theory that this and other quality issues would be improved if the firmware made the XYZ moves lag slightly behind the extruder moves. My thinking is that there is a significant and reasonably fixed delay between a change in the extruder motor speed and the resulting change to the speed of the flow of plastic. Making the extruder operate in advance of the print moves by the same delay would result in the plastic flow being more closely synchronised to the nozzle movement. I believe DC42 is thinking of experimenting with the firmware along those lines to see whether the theory is correct, though it is a relatively complex firmware change to achieve.
Simplify 3D slicing software (not free) has a feature called "coast to end". When enabled this results in the extrusion being stopped prematurely a fixed distance from the end of the current line, and the line is completed by the "ooze" rather than actively extruded plastic. I have found that that makes a noticeable improvement to the blobbing, though I have not experimented yet to establish that it is definitely that feature that causes the improvement rather than other differences in the way S3D slices. If it is the case however, it would tend to support the theory because it is effectively a partial implementation of what I have described.
Dave
