Character fusion and new hero class: The Mutant
How it works:
a) Bring a character to level 90
b) Bring a second character to level 90
c) Do the same for a third
a) Character A visits her trainer and tells her “I’d like to use a Spec of this character for fusion”. The trainer hands out a 'fuse'.
The same happens for all 3 characters and 3 fuses are collected
b) The player creates a new character of the new hero class: Mutant.
The player spawns into a super-secret laboratory controlled by a faction of ingenious goblins and gnomes using Titan technology.
Your caretaker finds in the mail the 3 fuses sent by your friends, the other three characters.
A new super hero is born, having as spec 1, the spec from the first player, as spec 2, the spec from the second player, and as spec 3 the spec from the third player.
Now, let’s not get ahead of ourselves and get overexcited; there is a loot distribution issue to handle due to the complex nature of the Mutant setup.
1) A new “Mutant’s” token drops that can be used to purchase any of the class’ specs the Mutant possesses but no other. It is also unusable by the other classes that have the specs it originates from.
Also, since one could say ‘There is no reason to not play a Mutant’ (and the Mutant tokens would be in high demand):
2) Loot will be finally dynamic to reflect the number of each class on the setup of players. It will still be random but not fixated to a predetermined chance.
PS. Dips on Fire Mage/Prot Pala/Disc Priest has been called
edit: Boley brought the good point of OPness due to the universal spells of a class being available simultaneously. This can be tackled by restricting the universal spells of class to be available only when a Mutant spec is enabled.