Mine is the kick-start model, with a listed dry weight of 248 lbs. Two gallons of gas, two quarts of oil, and two quarts of coolant add 24 lbs to that figure. Throw in the weight of a battery and starter motor, plus a few pounds of blinkers and wiring for the DRZ E and S models. They aren't the lightest out there, but are VERY competitive weight wise with a WR450 or similar. They are really only heavy compared to MX race bikes, or stripped down 2-strokes. Also the valve clearance service interval is a generous 10,000 miles, coupled with other service items more typical of road bikes, and I get about 35 miles per gallon OFF ROAD.
If all you need is a lightweight trail bike, get a 250cc+ 2-stroke MX bike and gear it down or add an auto clutch. If you want something you can ride to the trail and then on it, or even longer stretches of highway between trails, pick something like a DRZ. Just understand that any feature you add (street legal, etc) adds weight!
Jared