I have a 2009 IS250 AWD and have been lowered for almost 2 years.
I went with H&R spring kit, a modest drop of 1" and 1-1/4".
From what I understand, there is no risk of permanent damage to the axle but the wobble and vibration is insane. At very low speeds, my rear end wobles side to side and major vibration.
I also experience the vibration on drive but stopped.
I have looked into various solutions with no luck.
I hate the look of the stock springs but I can't tolerate the poor ride.
I am seriously considering selling!