Another way to get some good DR relatively early on is going Warlock with the Fey Heritage feat line. Human/Strongheart Halfling and flaws let you accomplish decent amounts of DR/cold iron quite nicely by, say, 8th level. Warlocks aren't totally fragile, and some of your Invocations will require you to be at least close to the front lines. Paired with DR 7/cold iron, you'll survive most things that could hit you - while you're exploiting Fell Flight to be safe from charger builds.
DR of any kind is best paired with two other things: a) the ability to endure at least a little HP damage now and then (like not being a Con 8 Sorcerer), and b) the ability to avoid the most HP damaging kinds of attacks, like charges (flight works wonders here). If these conditions are met, even mediocre amounts of DR can be worth it: you'll avoid the really big hits, and the small ones won't bother you at all.