I was wrong, but you were even more wrong:
Twin Rogga: 300 base damage * (1 + 220%) Hornet Strike * (1 + 180%) multishot = 2688
Tigris: 1050 base damage * (1 + 225%) Primed Point Blank and Blaze * (1 + 120%) multishot = 7507.5
The Tigris ends up with 2.8 times the Twin Rogga's damage after applying damage and multishot. No other relevant mods scale differently between pistols and shotguns, so that 2.8 times more damage will always stay as 2.8 times more damage.