Thorns:
While I agree that it is very powerfull for farming lower mobs - it is just that. It just gives you some councils. No usefull items to wear. If you want to farm high level elites there are way better ways than doing it with thorns and in most of the cases it didn't work anyways.
Fairy:
The only thing that prevents me from useing it as an real alternative to my main is the death penalty. Just one thing to think of: Maybe don't put nearly all advantages of the fairies at the "outside of fighting" situation (skill unlock, space, flying, food) and the disadvantages on the "during fighting" situation (death, metal amor,). Because in most cases skill sets/races/what ever is compared on the performance in battle. While it is very nice to have ice freely unlocked it is "just" saving "some" time at the beginning of your character. On the other hand if you die it will costs you time all the time (doesn't matter if you spend the time on farming the resurrection items or running back). So the battle advantages are the fairy magic skills. But you only get them while useing mentalism. So useing a fairy without the mentalism skill set is a very hard decision. Maybe let the fairy magic skills still be unlocked through leveling up mentalism but useable with all skill sets but with a (25%?) penalty if mentalism is not active.
If sticked to mentalism skill set: Maybe let atleast 1-2 of the 4 fairy magic skills be useable from the sidebar as an small benefit. Because if you want to use mentalism you allready had the harsh situation that you have not enough skill slots (same with all skill sets, but mentalism suffers a bit more of it because of the waves). So the new skills would only add a very tiny benefit because you have to throw another skill away for them.
Stun locks:
Suggestion For mobs: after the first stun hits them and has last, the next one only lasts 50% of the stun time and so on and if you stun one while it is allready stuned it reduces the original stun by half.
Assuming a stun time of 4 sec's it would be in the first case: 4sec + 2sec + 1sec + 0sec as the maximum time you can stun the mob regardless of fighting duration.
Assuming a stun time of 4 sec's it would be in the second case: 2sec (halved) + 2sec if you stun him two times directly one after the other.
Assuming a stun time of 4 sec's it would be in the second case: 2sec (halved) + 1sec (halved) + 1sec if you stun him tree times directly one after the other.
Suggestion for players: First stun works as it is now and after it the player gets a stun imunity of the same time.