What's the Next Guardian?

By going through the previously released guardians we can get a better idea of which unique guardian element we may see in upcoming patches. The class of that guardian is going to be dependent on that class's element. For instance, they wouldn't release a unique tank on an element that already has one (at least for now). Nonetheless, below is a list of the most recently released guardians for each element and class type (i.e. Tank, Support, Ranged, Melee).

The most likely next element would be as it's been since it's last unique guardian introduction.
Alternatively, it has been since has had a new unique guardian so that is also a possibility.