Mate, you could’ve just hit the search button and typed in “shotgun” 
My opinion: I don’t think shotguns are balanced. They’re too limited in terms of armour types you can engage with in basic mode, and the special shells take too long to activate … and are pretty lacklustre even when you do.
Add on to that the inconsistency in damage. Oft-times you shoot a (say scab) target, it sprawls on to the floor, then you have to fire again (and maybe again, as floored targets seem to have a weird hit box to me?). If you can’t one-shot scabs every time with centre-of-mass then it’s too unreliable for me! 
I’ll stick with a brauto or iag thanks. Or even the ironhelm; I love that on my zealot.