I was originally going to pop in and defend 3.5 DR, but now that I think about it, I think it depends on the case. If you're trying to create a setting in which all magic comes from the same source, and all monsters are fundamentally the same type, then having some of them have Cold Iron DR and some have Silver DR and some have Admantine DR doesn't make a ton of sense.
A fellow RBDM is running a campaign in which the Fey are pretty much the main monsters in the world, and every monster is probably either a Fey or a Fey-touched creture. It might make sense for the Fey and Fey-touched to require different material to really hurt them, but you could also do it with one big type -- like saying that Cold Iron cuts through the first 5 points of DR and Mithril cuts through everything, and then you give the Fey-touched DR 5, so that Cold Iron hurts them, and the Fey get DR 10, so Cold Iron helps a bit but not much.
That's in a campaign with a specific setting, though. In a general D&D campaign, I see no reason that a werewolf hunter should be well prepared for an attack by golems or fey or devils, so I don't see a reason why having him be S-outta-L with his silver sword when that golem shows up is a bad thing. As others have noted, he can power attack, trip, and do lots of other tricks in this edition that will help him out.
This sounds a little bit like a player who makes a fighter with no ranged weapons and then complains because dragons have fly-by attack. The problem is not with the system. The problem is either with your character or your DM, or more likely a combination of the two. If the PCs get attacked routinely by stuff so powerful that the PCs NEED max'd out focused weapons, then they are right to complain if they are attacked by something just as powerful but focused in a different direction. That's not a player problem. That's the DM getting into an arm's race with his players.
But I digress.
