I'm not sure if this is intended, but it is possible to 'stack' the primal AOE spells and get two of them to fire at almost the same time.
For example, click on 'blast', and before it finishes casting click on 'barrage' to queue it for the next attack. 'blast' will run the full length of the spell cast timer, and once finished 'barrage' will go off instantly.
This seems to work with any combination of the AOE spells.