Can I use the rock slider/steps as jacking points?
I have not seen anyone do it but I am going to say no because you won't be able to get close enough to the body to allow the Hi Lift a good hold . . .
Uh, according to voyager offroad site for their rock sliders and their product photo, you can...
I checked out the product photo, and it shows a Hi-Lift used on a slider with a step. I'm thinking that if you have the version without the step, you are totally out of luck.
About Hi-Lift jacks:
They can be extremely dangerous. They are best used with some training and practice. At minimum, get the Bill Burke recovery DVD. Hands-on training would be better.
The most obvious issue is getting smacked in the face with the handle as you lower the vehicle and the handle slips out of your hands. Good way to loose some teeth.
Another less obvious hazard— You get stuck in mud or snow or on some loose dirt. You pull out the Hi-Lift and start jacking up the truck. If you are jacking up from the side, as the vehicle is lifted it will want to move sideways away from the jack. If it does, even a little, it will change the angle of the jack relative to the truck. When you lower the truck, the upright member of the jack will make contact with the door, scratching or denting it. It happens often enough that you will read advice to raise the window glass before using the jack so that if the door is crushed at least you don't break the window inside the door. The worst part of it is that once the vehicle slips sideways, there's nothing you can do about it. Your only choice is to lower the vehicle and watch the bodywork take a beating.
There is an accessory that allows one to lift the truck with a Hi-Lift jack from the wheel itself. It helps to get the jack away from the bodywork. It's called a Lift Mate. It is good for getting un-stuck, but no good for changing a tire.
Perhaps a better option for the LR4 is an exhaust jack. They are sold under the brand names of X-Jack and Titan. Perhaps other names too.