The armour set things should be rare in my opinion..thats why i dont mind 3-5(depending on class) sets but thats it. So fighters set could be breastplate,2 handed weapon and helmet. Theif could have dagger,ring and belt and boots Ranger- Bow,gloves and boots Wizard...robes,staff and 2 rings.
Becuase we also have a number of unique rings and stuff(like boots of the vampire) then we dont need too may set items.
Guilds have been mentioned but i dont like the "restictive" parts of it..that is..if you join one guild that means you have to fight against rival guilds.
Maybe you can ony join a partiuclar guild if your stats are high enough..say 25 stat points in strength or something or fufill a minor quest to alow you to join!!