I like it when the fish hammer it. The light bite is much tougher to detect. I doubt it's you rig that's the problem as most trollers use some form of the C and C rig, the bottom bouncer (Kentucky Rig), or all forms double drop rigs. What rods are you using? Sounds like you're experienced with trolling, but if they swallowed it deep and you didn't see the bite, Id think either the rod tip was too stiff, or you weren't paying attention to them. You did say that you didn't Feel it, were you strolling? That's what we call it when you're holding two rods in your hands while trolling.