While having the Barrage trait on fireball staff (not tested on other staffs, maybe same problem there, too) and getting the “barrage-meter” up using only one of the attacks, p.e. the single target fireball, and than switching to the charged fireball, i need one extra attack of the same sort to keep the meter up.
It sometimes will even work the first time, but not the second time. It happens the other way round too, first only charged attacks, then not working with the single target ones.
Barrage in general seems to have hick-ups sometimes, not registering hits. It is also not triggered by indirect hits, like the AoE-dmg of the charged fireball, although i don’t know if that’s intentional, your pick.
Here are two videos, but you need to download them, not working on OneDrive:
I’m sorry for the quality, first time ever recording and uploading a video, ever.