I just did a shoot of one of my rescue dogs using my older 5D Mark-2 camera, 70-200mm f/4L IS lens and EX 600 RT flash. I had taken off the Herringbone wrist strap from the 5D2 and placed it on my 6D2.
I often need to shoot one handed so I can attract the dog's eyes by waving a treat or toy over the camera and I realized that it was more difficult to hold the camera/lens/flash package without the strap than it was with the strap. Making small adjustments in framing was also difficult.
It is not the total weight of the package that bothers me; rather that the package is front heavy. In fact, shooting the 6D2 with battery grip and the same lens and flash plus the Herringbone strap is a lot easier than shooting the 5D2 package without battery grip or strap. This is because the extra weight of the grip seems to balance the unit and, of course, the strap gives me extra assistance in holding the package.