Well. I'm assuming you're specced Suppression. Your best bet is to just fight them like you would anyone else, spam lifetap and kite while your pets dance on them. Sprint around, since an assassin without endurance (assuming he's solo) is going to have a hard time killing anything.
Hard fact of the matter is that stealthers are designed to pick off casters pretty easily. That's why you're such a popular target, you're considered an easy kill, especially with your kobald constitution. My best advice would be try not to solo.