yeah ideally shooting things that are immune isn't good ^^
I try and switch when I see things go immune and act accordingly but sometimes if I notice my second char is in an awkward position to switch target or something then I just stick to the target, knowing it'll bite the dust as soon as its vulnerable then take care of the other player, this works if I know I can take the hits meanwhile (like if I have deterrence and other defensive CDs ready).
