Are "Sets" worth while? It seems to me that by the time I have enough pieces of a Set to do any good, that I have found armor/weapons etc. that are far better than the Sets.
I find them somewhat usefull. I have Taar set up as a nature mage/ melee character and she is using 4/8 of Lorethal's Legacy set and finding it very handy. I have also just started using 2/4 of Frostheims on Lothar, and he really tears it up. So i guess depends on some luck of when you find them.
It's a tribute to the balance of the game that you'll often be in this position. Some Unique Items (eg. The Ageless Hunter ranger armour, armour 426, +110 Dexterity, +300 Health, +200% Armor, +2 to Ranged Skills) have better overall stat multipliers than a whole set.
My characters don't have any complete Sets on them; I just mix it up using the general rule of thumb - "Max out!"