You mean as opposed to 3.0, in which DR was basically irrelevant due to the fact that everyone either had the requisite "plus" of weapon or had GMW up?
I have absolutely no problem with impenetrable DR combos. Creatures have to pay a substantial cost to get good DR, and all it does in 3.5 is shave off 10-15 points of weapon damage, which by the levels they're getting it is no big deal. After all, such creatures in many cases are already shaking off spells with some regularity and ignoring big chunks of elemental damage, so reducing a fighter's average damage output against them by 20 or so points a round doesn't seem like too big a deal.