The death was forced, it could have been done in a better way if they wanted that, but it wasn't too bad.
Charlie was pretty sweet and all and they could have probably done more with the character but it was ok storywise i suppose.
They fridge her bad tho.
Also the repitition, this is exactly what happened with Kevin, a seceret then a sweet decoder dies.
Though the nerfing of Cas is actually useful because it raises stakes why would Cass not be able to bring her back to life? Gadreel could.