Pattern is easy to read actually. 4th healer to stay in balance with 4 tanks. And a melee DPS to balance out the roster since it's currently 8 melee and 10 ranged. If you add the 2 classes you have 9 melee and 11 ranged.
And if you are a stick in the mud and hate BLU you can argue that there are going to be 9 melee and 10 ranged and 1 limited.
And that's 20 job classes. Game has come quite far.
