With the most respect possible, what a load of utter drivel.
S2 scattershot is great at dealing damage, especially in the early stages of a campaign.
1 to 6 automatic hits that wound on a 5+ is most certainly not useless for dealing damage.
Again, the ammo roll is better and you get the advantage of being able to guarantee hits and thus pins on multiple models.
Throw in Firestorm and you get S5, AP-1 Blaze.
For a character that wants to get up close and personal and be able to reliably continue to use their weapon and not have it become an expensive club the first time an ammo check is required, the combat shotgun is the go to weapon of choice.
My Goliath leader with his trusty combat shotgun has done serious work in the past, and I've tried many variations on the theme, including armed with a Bolter (Which is still a very good choice).
Not that the Bolter is bad. I loves me some Bolter action but for this particular character who should be leading from the front, personally, I think the combat shotgun is the better option and to high handedly declare that it is worse in almost every situation is hyperbole at best.
There's more to winning games than just raw numbers on a spreadsheet. Putting this guy into a position where he's a potential template threat puts your opponent under pressure and forces them to make tough decisions. Even if you hit with the template and fail to kill, do they stand up and try to shoot back? Do they stand up and run away? He's T6 with 3 wounds and nerves of steel. If you don't kill him, you're getting charged and probably torn apart. The more tough decisions you force an opponent to make, the more likely they are to make a mistake.
Leaders don't exist in a vacume either. They have a whole gang behind them. Do you shoot at the rapidly closing boss, who's supported by a couple of forge born, or the infiltrating Stimmer with incendiary grenades? What about the Missile Launcher toting forge boss who's rraining hell down on the gang from afar?
So, in summary, bolters have their uses and their limitations. Combat shotguns have their uses and limitations. How do you want your gang to play and what do you want your Leader's role to be within that playstyle?
Personally I've found Goliath to be a great short range shooting gang that like to mix it up within 12" to melee range (With some heavy support) and have had great success playing that way.
Your mileage may vary.