If I ever got into WoW again, I'd like to see "Trials".
What these are is a sort-of solo instance that tests your knowledge on the gameplay and tactics that surround your class and its builds. These would be Daily quests and would be given to you by your home capital's trainer, but would not count toward your allotted limit of Daily quests. Should you die during this solo, the quest will count as Failed, you get teleported out of the Trial instance and you must wait until the Daily reset to take the Trial again. Gear damage would apply normally after death, though you would NOT receive the stat and health/mana debuff after dying. The Trials are no joke and you will need to be well geared and somewhat versed in your builds in order to complete them, especially as you get to second and third level Trials.
If you succeed, you'd get a piece of Trial gear of your choosing, which would be slightly less powerful than the standard 25 man tier gear but slightly more powerful than the 10 man tier gear stat wise, however, it will have some set bonuses that tier gear would not normally have. It would also be unique in its appearance, kind of like the old tier gear of vanilla days of yester-decade and the color of the lettering to signify that it is Trial gear will be cyan, much like Borderlands' pearlescents. The gear would consist of Head, Chest, Waist, Hands, Legs, Feet, Shoulder, Wrist, Off-hand/Shield and Main Hand/Weapon. To obtain the weapon for the complete Trial set, you would have to complete all of the trials for that level of Trial gear AND complete either a 10 man or 25 man raid and obtain an item dropped by the end boss for that raid. The quality of the weapon obtained would be determined on which level of instance was completed. As WoW has normally had three levels of Tier gear, the same would apply for Trials as once you complete the first level of Trials, you can work towards getting the next level of Trial gear, with the challenges presented to you increasing in difficulty from one level of Trials to the next. All gear obtained through Trials will have, at the very least, one socket for gems. When a Trial is completed, you can choose what gear you get for whatever build you desire. For example, if you complete a Paladin Trial and the gear you get to choose from are all Chest pieces, you can choose between a Prot Chest, a Ret Chest or a Holy Chest. The set bonuses from the Trial gear will also reflect the build you have chosen, as well, such as added health/defense for Prot pallies or added mana/spellpower for Holy pallies. The set bonuses will be given at the even number intervals, with the complete set bonus being a considerable boost to a talent or having a unique activation upon an event. Once you complete a Trial and receive the piece of gear, you cannot "redo" the Trial for a different piece of gear, meaning if you choose Prot pally gloves, you cannot take a Trial for another set of gloves, so choose wisely!
Also to be included in these trials, exclusively, is the slight chance to receive items related to professions upon succeeding a Trial! Be it Blacksmithing, Enchanting, Tailoring, etc., the item would be yours to learn should you possess that particular profession. The item for learning how to make it would be Bind on Account; however, the item itself would be Bind on Equip, meaning that you would be able to sell, or give away, what you've made. Enchantments learned in this manner would also mean that you could enchant other people's gear as well as sell them on vellums.
This would encourage people who do not wish to raid all that often to have some chance at getting quality gear, as well as the Trial exclusive profession talents, on their own without the need for depending on others and having to fight over gear. This would also test the player's skill and knowledge with their class' abilities so that they would gain a greater understand of what their class and builds are capable of instead of "make this build" "spam these moves" kind of tactics. To ensure this, the Trial instances would be varied to the point where different builds would be more effective for the current Trial than others. The trainer will offer a skill point reset, at no charge, before each Trial begins and give the player an overview of what he/she can expect so that if a reset is needed, the player has an idea of what to expect and prepare accordingly.
With this, the player would get a sense of accomplishment through their own abilities, add to their knowledge of the uses of their builds (potentially) and to be capable of performing well in end-game content without going through heroics and depending on others for the chance at gear that they might receive, though having heroic gear for Trials wouldn't hurt in the least.
EDIT: Just thought of something else to add to this - by completing all levels of the Trials, you get an achievement called "Mastered Exploder", a completely decked out fast mount from your home capital's mount trainer (cyan lettering with this one, can have one passenger) and a miniature version of yourself in full high level Trial gear as a companion, aptly named "Mini You".
(WHEW, that gave me arthritis twice typing all of that.)