Well when I see a 2.5 modifier I view it as being really 2 hits of 1.0 modifier. So if CDC is a 2.5 for the first hit and 1.0 for the extra 2 hits, it's really similar to Vorpal which is 1.0 for 4 hits, and I've seen some awfully impressive CDCs in VW that exceed or match something like Drakesbane which is done from a weapon with double the base damage, where attack shouldn't be an issue with Bard and Stalwarts.