First of all: Welcome to the forums!
Most important answer first: Yes, it will get better. You just need better gear.
Now for the details:
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Switch back to “normal”. “Veteran” is pretty challenging (IMHO it’s overtuned, but maybe that’s just me…). The 10% more xp you get are never worth the hassle. For leveling up, normal is the way to go nowadays.
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Don’t be afraid of the change to Elite. In fact, the transition from normal to Elite is quite smooth. Except maybe for Warden Krieg and later on Darius Cronley, enemies at the beginning of Elite aren’t really hard. Besides that, you’ll also get better gear. It is definitely doable.
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Infltrators aren’t exactly the easiest characters to level. But you got the Inquisitor mastery. If everything else fails, put as many points as possible in Word of Pain and maybe some in Storm Box of Elgoloth, get spells from components and play as a caster. This works well at least into the 50 level range. I don’t think this will be necessary though - which brings me to my next point:
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Get better gear. I know this is easier said than done, but you need more resistances. That extremely low Aether resistance for example would get you killed against any enemy doing Aether damage, regardless of the build you’re playing. Focus on gear with lots of resistances. Even in normal, there are rings, belts, boots, gloves and so on with a lot of resistances on them. Crafting isn’t too expensive either. Make resistances your top priority.
Don’t give up. 
You have an excellent guide to follow and you’re playing a very fun class. Good luck!