It sounds like a problem with your setup.

I recently built a soma double cross with avid road bb7s, and Tiagra brifters. The brakes are great, and noticeably stronger than any canti I've used (avid shorty, tektro oryx, tektro cr720, shimano br 505). They don't grab as fast as v brakes with the matching linear pull road levers, but the modulation is better, and they can stop me just as fast.

I am using compressionless housing and normal brake cable. One thing I noticed early on, was that turning the inline barrel adjuster on my housing a bit to tighten up the cable slack really made a difference. At first I set the brakes up with the pads as close possible without rubbing, and did some riding without messing with the barrel adjuster. I had to squeeze the lever a bit before the brake started catching. I turned the adjusters to tighten the cable until just before the pads rub, and the brake grabs much sooner now.

I would try reinstalling the brakes on your own, following these instructions http://howtosetuptheavidbb7.weebly.c...-avid-bb7.html