I'm having trouble killing Salvarola in Kingsward - I'm a couple levels behind (58; Salvarola is 60), but haven't had any problems with the quests before him.
I main Pyromancer, but that generally has single-target DPS; Salvarola is a summoner boss, but targeting the minions first prolongs the fight long enough for Salvarola to kill me, whereas leaving them unchecked multiplies his DPS far too much.
The only alternatives are stunning the minions or using Fire Storm, but they'd recover very quickly unless I used Transmogrify (which has too long a cast time that's only prolonged by Salvarola and his mutants attacking me while casting, and only takes out one of the two), and Fire Storm has too low damage to be of any use.
In short, no matter what I do, Salvarola wins.
My points are specced as such:
13 Stormcaller (5 Storm Energy - 4 High Voltage - 4 Cyclogenesis)
3 Dominator (3 Clinging Form)
58 Pyromancer (0 Fiery Concentration - All others maxed)
149 Attunement of Fire (All maxed except Tier-3 Sword and Dagger Mastery)
After asking in chat, someone suggested I play Stormcaller, but so far I can't figure out how to play that effectively. Testing on the mobs around the Tower of Dawn, it seems entirely inferior to Pyromancer, both single-target and multi-target even if I use the strongest available spells and appropriate Mage Armor for the situation. It's doubtful that the soul is entirely useless though, so presumably I'm doing something wrong...
My points are:
58 Stormcaller (0 Perfect Conditions - All others maxed)