Having played around with it a bit on Battle Wizard, the new staff does struggle to perform well when compared to Sienna’s other choices. It’s clearly trying to be something different, but the role it performs is outdone by other staffs.
Seeing as how the release version has such a short charge time to max size (that is feels negligible), it would possibly suit the staff to swap around the different spells. Having the flame geyster as the light attack wouldn’t change the way it is used due to the insignificant charge on it and its low utility, and give the flaming rocks more utility.
If the flaming rocks became the charged spell, the power/ stagger/ explosion effect would give the staff a much stronger role than it currently performs as.
This could be criticised as the beam staff already has a similar charged spell, but I feel the difference in fire DoT between the two makes up for part of this comparison. Furthermore, the rocks have higher stagger, which the beam makes up for in it’s light attack ‘punch’, and not the wide blast, which also has little difference in power when charged, at least from my experience, thus they still would not be as close in comparison and my suggestion can plausibly give the Coruscation staff a more respectable role.