A couple things to understand about shock design and lift in relation to our panhard bar:
1. A twin-tube shock design puts oil and N2 in contact with each other. If this is what you're currently using (most stock and inexpensive setups do) then you'll only get so much control out of the shock until the oil starts to aerate and exponentially lose dampening with it. A monotube is preferable for non-paved usage because it separates the air/N2 from the oil - an external reservoir monotube design goes one step further and takes the air/N2 out of the main tube completely for additional travel capabilities (along with greater heat dissipation).
2. Although heat build-up is a minor concern next to aeration, washboard roads tend to be the #1 culprit of heating due to the consistent and excessive movement it provides to the shock. A budget-centric shock generally won't consider prolonged heat build-up in their design, which can also degrade the consistency of the ride.
3. If you are lifted more than 2" then your panhard (rear lateral) bar may be causing excessive side movement of your rear axle due to its centerpoint being altered from the lift. This video explained it perfectly for me:
https://www.youtube.com/watch?v=liR1--EHMg8