It seems like as soon as there’s a callout made, it’s too late to pre-emptively kill them before they attack… either the gas rat has already thrown his bomb (or two of them, I don’t know if that part’s intended), or the gunner has warmed his gun up and begun firing. This is especially bad on Legend, where spending even a short time in poison or under gattling fire can kill you off. Their attack speed is ridiculous as well, with gunners starting to fire at the player usually as soon as they’re visible, and gas rats sometimes hurling bombs as soon as they even spawn.
I think both the gas rat and the gunner should be more like they were in vermintide 1, with player callouts happening about 4-5 seconds before the special even shows up… they also should not be able to throw poison or shoot as quickly as they do now. Give them a short waiting period before they can first attack to give players at least a chance of killing them before they do their damage.