Meh, the shops around me aren't any better (actually, they're a lot worse) at adjusting hubs than I am.

I suspect that the play on one side but not the other is a bit of a red herring here and that the real problem is that the hub is too loose (hence, play).

If the OP isn't using one already, I suggest getting an axle vice. Others may disagree, but I've come to believe that an axle vice is pretty much mandatory when adjusting rear hubs because it's the only way I know to keep the axle from turning as I tighten down the locknut against the cone.

For those suspecting the seals are creating drag, these are 105 hubs, which don't have the aggressive seals of MTB. From personal experience, those babies should run very smoothly once adjusted correctly.

Mike