I'm a big fan of Joe Posnanski. he's one of my favourite sports writers and also a pretty good follow on Twitter. This is a great piece from a few weeks back about the potential for a better way to figure out which pitchers should get the wins and losses in a game.
As you can see, nothing in the history of mankind has wasted more words [the rule is 711 words long] than the pitcher win-loss rule. The rule made sense at one point — and was barely needed at all — because starters mostly pitched nine innings. But these days, starters almost never finish games. There are often three or four relievers pitching.
I agree that it has become a very flawed stat. It can be very arbitrary a lot of the time.
I started thinking about the same stat in football for quarterbacks, but that one seems to make more sense—at least a little—because the quarterback generally plays the whole game. It's still flawed because you can win 3-0 because your defence did all the work, but it's better than baseball's version of the rule.