DR in 3.5 is nowhere near as bad as 3.0, and any Archer/machine gun thrower build needs to find a workaround (and will do so). Fortunately, there are only a few things with more than DR 10, and almost nothing with more than DR 15. A thrower can use Bloodstorm Blade to retrieve a small number of reasonably enchanted weapons, such as Shadowstriking; while an archer has a few enhancements like Force from MIC that make DR a non-issue. As for DR X/- and type specific DR, there is the Sense Weakness feat from Draconomicon, slicing off the first 5 points no matter what for your Focused weapon.
TL;DR The impact of Damage Reduction in 3.5 is way overblown in theoretical builds-by the time you need to regularly deal with more than 5 points worth, any build dealing Hit Point damage will have acceptable workarounds.