Collecting sets of items has a certain undeniable appeal to gamers. Whether you are collecting artifacts in Rift or trying to complete the latest tier set in WoW, there is a compelling quality to the system that makes you want to keep collecting. This is good in so far as it keeps players interested in loot and I consider interesting loot to be an important part of modern (MMO)RPGs. The thing is though, that it is really hard to get rid of a set of items once you have it. Set bonuses often make subsequent gear improvements pointless because swapping out one piece of gear would cost you those bonuses.
I just experienced this once again in LotRO. I collected a set of items in the 30-40 zone of Evendim and only just dared to replace it at level 50, having collected and stored away individual improvements ever since so that I could make the big swap at one point and not get worse due to it. Even with the simple set bonuses I have seen so far (just stats), swapping out so many pieces of gear at once tends to be too much math to simply do in your head. Either you resort to outside help (be it spreadsheets or a piece of paper) or you take an educated guess as to when the individual improvements outweigh the lost set bonuses.
I don’t mind a bit of math at the endgame at all, but during leveling I really don’t want to be forced to get outside help. Sets add a burden to player itemization decisions and at the same time devalue other loot drops that might be exciting if they wouldn’t break the set. I’ve gone 12 levels in the game (almost 1/5th of the total leveling experience) without getting any real upgrades to my gear. It is a bit sad to see all those NPCs spending their last coin to reward me with rare items only to then turn around and stash them or vendor them right away.
My first experience with item sets was in Diablo II as far as I can remember. There, set drops were exciting (up to a point) because they were rare. It was, in fact, rather uncommon to see people wearing a full set. Instead you would pick up two or three pieces and fiddle around a bit with combinations to see what suited you best. In most cases it was quite possible to find upgrades that made breaking the set worth it.
Later on, when I had access to a large pool of items, sets still kept things interesting. I would know, for example, that I wanted the two-piece bonus of a certain set. I would then go on and find the two least-valuable slots that I had otherwise and try to fill those with set items for the bonus while wearing individually strong pieces in the other slots. Wearing a full set often wasn’t worth the loss of potential in other items.
MMO sets often fill neither of these conditions. Most of the time it will be obvious how to collect your set pieces (You’ll know which boss they drop from, which quest they are rewarded for, or which currency to buy them for.), they will not be particularly rare, and wearing the full set will more often than not be the right choice. This makes the decision as to what to wear both boring and unnecessarily math-y.