Does anyone remember a post several months to a year ago that Sigma dock AF Microadjustment is like 2:1 vs Canon AF Microadjustment?
I do, but in my experience "...is more what you'd call 'guidelines' than actual rules" as Captain Barbossa would say. The value is a good starting point if you have already done MFA via the camera, but there are so many more variables such as multiple focal lengths and also focus distance for each of those focal lengths via the dock, that you are best marking out targets at appropriate distances and adjusting each and every one. Make sure you reset the camera MFA to zero for that lens before you use it to make dock adjustments.
Do bear in mind that the dock settings interact somewhat, so use the "guidlines" quoted as a starting point. Set the intermediary focal length adjustments on the dock to be on a suitable "curve of values" that link the 150 and 600 settings from the original camera MFA (x2), and fine tweak until you get bored. It's well worth it IMHO, but VERY tedious. You will also need (as per camera MFA setting) more than one shot at each of the settings to get a median value for the true setting due to mechanical slop inherent in any lens system.
These are what I got on my 6D which I use as reference for all other bodies I use the lens on. (Sorry, can't get a proper table to show, but you can see the values)
F.L. 2.8m 6m 14m Inf.
150 09 09 08 08
250 11 11 10 10
400 13 13 12 12
600 16 15 14 14
If you use more than one body, DON'T adjust the lens via the dock again, just use very basic MFA on that second/third/... body, keeping just one camera body as a reference for all Sigma dock adjustments.
Hope that helps.