They really need to add weapon testing. I got the Steeled Veterans wb for the flame breaker and it turns out I fucking hate that gun. Now I'm out the 1000 SC I grinded for
You should give the incendiary breaker a second shot, it is the best shotgun in the game and by far the best weapon against bugs, as long as you have a good support weapon for chargers and titans.
I run IB/Grenade Pistol/Incendiary Contact nades/Quasar in diff 7 and 8 missions and am usually above 250-300 kills per mission.
I think I prefer the slugger against bugs, tbh. Requires more aim but you can shoot right through most armour. Makes it way more economical to kill armoured bugs.