I have been reading this for awhile and as a bomber here are my ideas to make it so chaos is more glass cannon like without messing up mad bomber.
1. As some have said making it normal only would make it more glass like, but I feel it would still be strong even then. Maybe instead of having only normal defence giving it only elemental defence(it makes sense as its a magic set). This way the Chaos set can keep the VH bonuses but will make people more careful as they will die a lot faster.
2. Give the set only a universal high bonus fro CTR and DMG. This would be done by giving one piece a low CTR and a med DMG while the other piece has the opposite. This will make the mad bomber more useful for bombers again and chaos useful for everyone(mainly hybrid players).
Both of these changes will make the set unique but still usable by all three types of weapons. Now I know my ideas will upset people but with a hybrid set like this you have to think of other more specialized sets. Specialized sets should always be more powerful, it is the same way normal and split damage weapons compare.
Sorry if i wasn't clear.
I was saying that one way to set Mad Bomber apart from Chaos would be to change Mad Bomber's defense from elemental to shadow (Mad Bomber, not Chaos). The revised Mad Bomber set would offer defense against normal and shadow damage.
Though you are correct in that this change might conflict with the Mad Bomber Mask's description.