DoutPower

Ahh, that makes your intentions quite clear. Rather than really decoupling the grounds you are "offering" the current a low resistance path.

I am offering a low resistance path but I am also trying to make sure that the power surge doesn't get introduced directly into the ground of the logic.  Under idea conditions the POWER + and - lines of all the DoutPower bds will go to the high current power supply that is floating and not grounded.  There is a jumper on the board that can be shorted out that connects the Power - to the logic ground.  The only jumper that should be connected is the first one in the Dout chain.  This stops any of the high current surges from flowing thru the logic grounds which can upset the shift register states.