I'm a 50 Inquisitor now..
If there's one thing I've learned from playing as an Inquisitor, is that it requires you to absolutely use and know all the skills the class has. Electrocute, Jolt and other interrupts are your friend. Use them.
Also, the choice of companion is pretty important.
Since you're a sorcerer, you'll need a melee-tank like Khem.
However, for boss fights, I went with the Healer companion. You don't have him yet, though. But as a sorcerer, you can heal yourself and your companion too, despite not having the right talents.
Lastly, in your preferences, you can click 'allow other players in my story area.'
This means others can help you, although the area is supposed to be restricted to you. This is a great help for the hard Inquisitor quest. And believe me, they will become much, much harder.
"I think the Devil ****s Dutchmen."