So right now the meta wiz strategies seem to be spam and vent or simply using the heat sink trait.
You made a slight tweak on the beam but still with a high crit build you cant vent incredibly fast with random beam blast or simply holding beam and rocking the beam over a crowd (this will also increase the ulti generation bar incredibly fast). Same goes for bolt where you still can vent incredible fast on lmb attacks into crowds.
My suggestion would be to bring back earthing and nerfing temp health for staff kills. I would also suggest NOT to make the earthing a crit build kind of thing. Either keep it as a guaranteed heat vent on kill/hit but keep it small. 0.5 heat per kill/hit or even less.
What I am saying is not to make this trait or property a crit activated thing in which traits/talent rely on crit and instead make it just a procentage as in v1, making it simple to balance.
Sienna needs a bit more interactive gameplay than simply spamming staffs into crowds and then stand back and vent. This is mainly a melee oriented game and rewarding sienna for melee combat is both fun and (possibly) easy to balance.