I have seen a number of people in the MMO blogosphere posting lately about random bosses. The general gist of the posts is that the current model of boss fights is poor and that a new model incorporating random abilities instead of static abilities would be better. The basic premise is that a boss that has the same abilities each time you fight requires a very specific set of moves to defeat and once you master those moves the fight becomes dull and uninteresting. The players advocating this position usually think that once you know the 'dance steps' to a particular fight there is no more fun in doing it.
The model they often suggest is one where you zone into a dungeon and meet a totally random boss. This boss would have a number of abilities chosen from a large possible list - 5 abilities from a list of 50 or so. The idea here is that you fight this boss, get some loot and then go on to the next boss who also has 5 completely random abilities. The theory goes that this would continue to be fresh since each fight is different and you can never feel like you have all the moves down. Week after week you would see new things and new combinations of powers from the random bosses that populate the dungeon.
I think this theory is dead wrong. There are a number of reasons for it but one of the big ones is the unnecessary demonization of practice. Doing something over and over again until you become good at it is the core of learning. It is how we learn to read, how doctors learn to heal people, how plumbers learn to fix drains and how video game players learn to beat dragons. One of the great joys of life is to do something challenging that you are extremely good at - the feeling you get from doing so is called flow. Practice to become excellent at something is not 'brute force' nor is it timewasting, it is simply the way in which we learn and seeing the results of those exertions is enjoyable.
Another big issue with random abilities is tuning. With random abilities sometimes particular combinations are going to be dead easy to deal with or completely impossible. Because it is often difficult to tell right off the bat if an ability set is impossible or merely really rough people would be extremely discouraged at the prospect of wiping - there is no reason to think the fight is beatable at all! Of course the extremely easy combinations would simply lead to people getting loot easily, and those two things together would mean that everyone would be best off refusing to fight any tricky combo and just spawning bosses as often as possible to try to get one that is trivial.
The last major issue I have with this theory is the fun of the fight. You cannot have an awful lot of really interesting mechanics in a random list. Bosses have to do extremely simple things that are totally unlinked from other abilities so players must react in very obvious ways. Every add must be tanked and killed, every splat on the ground must be moved out of and every debuff must be promptly removed. You cannot have abilities that don't work that way because it would take forever for people to figure out what things actually do which means every boss has a very limited number of things that can be done and some incredible boss mechanics simply could not exist. Another fun consideration is lore. These random bosses are not referred to by NPCs or talked about in quests, they are just 'HUGE POWERFUL DUDE WITH GOOD STUFF' that is there for no reason. Lore is a minor part of WOW for me but completely ditching it would be a real detriment to the fun for many people.
I do think there are some ways Blizzard could introduce random abilities. Some bosses could have several abilities to choose from (think Chromaggus) but make them all thematically similar and have all of them work well in the context of the fight. Even an Arena type setting where you have one random monster to fight each week and he does random stuff would be all right as long as it is a sideshow to the real zones. Changing the base model of fights to include random bosses/abilities is a giant mess, but sneaking a little of it into the game here and there could be a nice change of pace.