I would have found a way, even if it took some time and effort, to keep the wheels on the ground.
Technically it probably won't hurt anything to lift wheels off the ground like that, as the jacks are designed to handle the weight. However, lifting it that high, and losing the stability the wheels/tires provide, can make things very shaky inside. Thats what I don't like and wouldn't want. That, and with one or both of the rear wheels off the ground, the parking brake isn't holding you anymore. RV could 'creep' forward or backward, putting a huge strain on the jacks to hold it in place.
If I can't raise the low side up high enough with blocks to get it level without taking a wheel off the ground, I'll get out the portable shovel I bring, and dig a small ditch/trench just in front of the wheels on the high side, and drive the MH forward into those ditches to drop down the high side some. I've had to do that a time or two. That is why I bring a small, portable shovel. I know some will say you shouldn't be digging like that on a campsite, but my answer to that is....If the campsite is that unlevel that I can't get the RV level with blocks...Wellll, then I'll do what I have to do. :)
I know many do it (raise wheels off the ground) and it usually won't hurt anything, but I've just never liked that. I avoid doing that even if I have to do some digging. Takes away too much stability when wheels leave the ground.