The only way I can think of that this would be intended, is that you are left running after popping war cry as often as you can, so your son who is doing the actual dps does a bit more.
Blizzard seems dead locked on making barbs a zdps support-class. This was functional in D3 since it only took you an hour or two to boost and gear a new character. But who wants to spend 50-60 hours levelling a support char?