I think that the option should be there where the players should be able to choose whether only the overall score counts, whether each game counts or whether both count towards ratings.

I think the only time where I would say it was unfair for the higher player not to lose ratings points for losing single matches in a series is with tiemouts but with the vacation feature here I would think that would be unlikely to happen.

Also, there is the danger that high rated players would only play series if the current rules are in place as they know they will proably win overall against lower rated players, making it harder for players to gain ratings points.

Also in the real world, players accept that ratings tend to balance out over a longer period of time with good results balancing bad. As the site on the ratings system says, if you have earned your rating over a greater number of games, the occasional loss should not affect you.