Your problem is undersized brakes, plain and simple. Les Schwab's only installs OE-equivalent parts, and I trust their brake work. Your experience is not not unique. The farm trucks I used to drive were all that way, and so were the tow trucks i used to drive (even as new as a 2003).
I actually don't know of a good easy solution. Better pads will help, but not a huge amount. My favorites are the NAPA Ultra Heavy Duty pads.
The newer trucks have better brakes, but I'm not sure how backwards-compatable the hardware is. Maybe somebody has retrofitted them on one of the Chevy forums.
Likewise, I used to have trouble going through front rotors on my van. I tried cryo rotors and just about every brand of performance pad. My ultimate solution turned out to be a new OE front-end off of a newer van. It was an easy swap for my rig, but I don't know enough about the chevy chassis to even guess it its possible for you.
