I think that genjutsu, EXACTLY the way it is presented in the anime, has potential to be truly awesome in mmorpg setting.
What I mean by exactly like in anime?
In anime they can only release genjutsu with that release handsing thing, IF they suspect that they are under effect of genjutsu. With releasing other people from outside being way easier than releasing yourself from inside. SO THEY HAVE TO CONSTANTLY BE OBSERVANT IN ORDER TO FIGURE OUT that they are UNDER genjutsu and ofcourse care not to get caught in it.
For example:
---Single target skill, when used on a player, makes him see illusion of the mob from this area(higher lvls make him see illusion of another player). This will result in him reacting to the illusion and noticing that his attacks go throw it/dont work the way the should/mob didn't spawn on his normal spot. Thus he concludes that he is under some kind of genjutsu and uses genjutsu release thing in attempt to free himself. To other players he would look like lunatic swinging at nothing(because they dont see illusion), just like in anime when people go crazy cause of genjutsu.
---Single target skill, when used on a player, makes his HealthPoints/Chakra/Shuriken&Kunai ammunition(any of those) APPEAR ONLY TO HIM different than they actualy are (HOW they should appear could be controled by caster (more/less than actual or fixed ammount)). Player would have to keep track of his stats or notice they aren't acting the way they should in order to conclude that he is under genjutsu. Thus he uses genjutsu release thing in attempt to free himself. Just like in anime when Sasuke made Danzo think that he still has 1 sharingan eye left for Izanagi, while he actualy had none.
---Wide area skill that affects all enemies/enemies&allies in certain range of the caster. It could inflict similar effects like skills above. Or maybe make all of those people see everyone around them AS enemy, however will game define enemy(red color or different headbands/clothes/equipment). Potentialy making whole enemy army slaughter themselves. Any of caught players could use genjutsu release thing in attempt to free himself if he suspects that he is under genjutsu. Experienced group of players would all easily see throw this genjutsu so it's not imbalanced(it would be more advanced jutsu).
---Any kind of summoning illusions that everyone can see, ik that there is no summoning in game, but this would only be models that you can walk throw(models of mobs or players). Because these would NOT be TARGET based, they could NOT be dispelled/released. You would need to somehow interupt caster to stop it.
---Zabuza's Hiden Mist, same as above, but instead of illusions makes fog in a certain area around caster. Fog removes sound effects created by players who learned skill needed to fight in fog, like Zabuza and also TO THEM appears less dense. Others get crippled by it. Fog size/range, visual density(which realy impairs victim's ability to fight) and stat bonuses improve with jutsu's level. This cant be dispeled, this would not be imbalanced because you can just run out of fog.
Basicly players could spam genjutsu removal thing if they were not sure if they are under genjutsu. But they would have to improve their skill at it to succesfully free themselves from stronger genjutsu. When they improve their skill at it, it's casting time or chakra cost increases, preventing them from spaming it like idiots.
Casting could also have many different requirements: draw target's blood, simply get in range, target standing still for few seconds, you not being hit/interupted for few seconds/certain time, knock target to ground, target keeping your character in his CAMERA VIEW for certain time(just like looking in to eyes in anime, certain time to balance it).
Some genjutsu when succesfully cast wouldn't show any visible animation, leaving target to figure out that they are under genjutsu. Others would obviously be visible(Hiden Mist).
How i read about kakai genkai in faq.You could add 1 like tsukuyomi, which simply deals instant single target damage when succesfully cast, but is classified as genjutsu. You could also add 1 that gives partial or complete imunity to genjutsu or certain kinds of genjutsu(some of your 20 jutsus).
Illusions seen only by affected players could easily be programed CLIENT side.
Sory for huge wall of text XD. LONG STORY SHORT, I dont want genjutsu to be some stupid stat changes or just damaging skills. I want it to be tools for playing with other player's minds. Just what genjutsu is supposed to be. Hope I helped.
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