Not a whole lot of need for shotguns in the current implementation, I agree.
If there were any special rules for shot vs slugs, especially shot with variable chole, or anything to distinguish them from rifles they might be worth considering.
They hit harder than SMGs, and have better Close ARs than rifles.
They do hit harder than SMGs (except the P93), but are harder to conceal (except for the short-barrel T-250). SMGs also have superior close Attack Ratings over shotguns, and rifles are barely behind.
The the CMDT, like the OP mentioned. It's DV of 4P is greater than most SMGs and equal to most rifles, but the AK-97 and FN-HAR both do 5P. Additionally, it's AR is 4/11/7 (with Laser Sight included); comparatively, most rifles are in the same range but have far greater range and therefore versatility, as well as Full Auto.
I just don't see any reason to bring a shotgun to a gunfight in the current rules. Let's hope the combat book changes that.