Macabre
Your Friend and Mine
Get rid of them completely. You shouldn't be forced to use certain weapons on them at all times. It's really restrictive. And it's not really a creative approach for enemy designs as well.
I think it's dangerous thinking to discard ideas outright even if their execution was bad; enemies with weapon immunity have been an element in the franchise before and still worked. Remember the Shadows in DMC1? You couldn't hit those arseholes with Devil Arms at all without getting a spike in the urethra. The game forced you into wailing on them with Guns before their weakpoint could be exposed.
I was thinking arround these lines but rather than braking a shield blue enemies would move arround quickly and dodging sword an demon attacks leaving you having to stunt the with the quick angel attacks. The red ones would be slow and tank like blocking everything but demon attacks till ether stunt or defence broken.
I like this idea. Imagine if instead of breaking your combo enemies who are strong to the element you are using got a little speed burst which forces you to be cautious with your combos instead of outright stopping them dead.