Problem is, sometime during patching PtW and/or expanding to Conquests, the Barb's search pattern
also got adjusted by accident, so that instead of doing what they were supposed to do (i.e. marauding across the map, chasing down stray units, and sacking towns), they only 'noticed' Civ-units when those units strayed across the Barb-units' NW/SE-axis (
there's a stickied thread about it in the General Discussions forum).
In PtW, this wasn't so noticeable, because the Barbs would patrol by default, so would find targets more often. In Conquests, however, the Barbs would tend to sit in their camps, chasing Civ-units only briefly, then 'forgetting' about them as soon as they got off the NW/SE axis.
Basically, setting NoAIPatrol=0 in the conquests.ini makes the Barbs a
little more dangerous again (although still not as dangerous as the Vanilla-Barbs, which search for victims on
all tiles in their 'radar-range', not just the tiles NW/SE).