Was discussing this with some people in my LS the other day, we definitely need more complete sets.

One of the coolest things about Monster Hunter (yes I'm going there again) was that each wyvern/boss had its own full set of armor/weapons that could be made from it and they all resembled what they came from. It would be cool for all the big NMs/bosses to have their own full sets to be made from them. It would certainly keep some of them relevant due to the number of kills it would require to get all the materials at the very least.

Aside from the NM/boss sets, I think we just need more sets in general. Some things you can piece together but are inevitably missing one or two pieces which is annoying at times.