Of all the things in gaming, Grinding is probably one the most annoying things, right next to Griefing. There is nothing I hate more than starting a new character in any MMO and knowing I'm going to spend the next however many days, weeks or months doing the same repetitive, boring thing over and over and over again, ad nauseam and beyond.
Funny thing is, it didn't bother me 11 years ago when I started playing UO. I was a pure crafter and I would spend hours on end, days, weeks just mining the hell out of every mountain in Britannia. And then spending some more hours just making the same armor pieces in the hope of getting that coveted 0.1 skill increase. And boy, was I happy...
Today, the mere thought of training another miner makes my skin crawl. Identically, the prospect of leveling another character in WoW or LOTR or any new/existing MMO is just a big fat turn off for me. Grinding is purely and simply not fun, not when you've been there, done that as much as a majority of seasoned gamers have. It's mind numbing and it keeps us from what we really want to get to: the fun part, the end game PvP or PvM.
I can understand why so many games use the Grind as a training/leveling method. The Wikipedia article actually covers fairly well a lot of those aspects so I will not bother repeating here. The problem for me is that Grinding, imho, is a cop out and fails to fulfill its real purpose which is to train the players.
In many of the Grind games, the training quests can be summed up as 1) go fetch, 2) go deliver, 3) escort, 4) kill X number of, 5) kill X number of to get Y amount of and last but not least 6) gather X amount of. How does any of these make a better warrior, a better priest, a better crafter, etc?
If I'm going to spend an extended amount of time "training" a character, I would expect that by the time I've reached the highest level, I would know how to play that template well, in all its complexity and uniqueness. And if I'm a new player, I would expect that when I'm done training that character, I would have a good understanding of the game world in which it takes place.
My first WoW character was a holy priest. As such, you would think the "Grind" would be focused on my class and require me to perform tasks in keeping with the role I would be playing during raids. So why have me kill thousands and thousands of mobs for weeks when I will hardly ever be doing that in the end? A little bit of it doesn't hurt, but putting me in situations where I had to manage my shackles, fears, fade, lifting debuffs and diseases, the whole while keeping larger and larger numbers of NPCs and myself alive in increasingly difficult environments would have helped me become a better healer. Wacking 30 panters, 30 Raptors and 30 Tigers does not.
But one of the First Aid quests portrays well what I consider a class/profession appropriate quest. If I recall properly, it's in Theramore where an NPC physician gives you special bandages and you have to heal a number of wounded soldiers ranging from mildly to critically injured. You barely have any time to think as you must quickly assess who most urgently needs your assistance because the critically will die fast. If you let more than a certain of your patients die, you fail the quest.
In UO, our training is also a Grind. But our world is so complex that even veteran players often forget a lot of the mechanics actually available to them. Some other tools are simply not used because players aren't used to them, don't understand their importance or are uncomfortable handling them. If they had been made part of their daily routine through training, they wouldn't be so alien to them. It would also be a good way to teach players, newbie and veterans alike, about the world they live in and make them familiar with things they may have forgotten or never known about.
Any fighter/hunter template should be taught the specials and abilities specific to their class. You're a mage? Then your quests/training should require you to demonstrate you have mastered the use of your spells according to your level: curing/healing self or 1+ other(s) (could be something similar to the WoW First Aid quest), Fielding (you must keep a certain creature from reaching a certain location for a preset amount of time using e-field or para fields. At higher levels, you may also need to keep an NPC alive by healing/curing and casting walls to prevent enemies from casting on him), Dispelling (enemy fields or summons to make your way to/escape from some area), etc. If you're an archer or a dexxer, have quests with objectives that force you to use your various specials/weapons, from dismounts, to mortal, to moving shots, to chugging (arm/disarm macros), to healing or cross-healing using bandages, spells... And while at it, quests that show you were you can gather arrows, bandages, etc.
Crafters, such as tailors, should gain skills/experience from gathering the raw materiel (picking cotton in fields, sheering sheeps, gathering leather...), transforming those materials into cloth with the spinning wheels and looms. Have objectives that range from creating dyes (we need that!), dying specific items, crafting/enhancing others, and (if I had my way!) forced out into danger zones to harvest magic resources directly off the back of live boss monsters.
If training/leveling was more oriented towards teaching players how to play the characters they made instead of making them read play guides, I strongly believe it would be seen as less of a chore and definitely not a Grind.