Hi - to be honest we see problems with road springs breaking across all Mercedes models, if the springs have broken then this is not just a problem with the ML but across the complete range.
Mercedes say that the UK is more of a problem than any other market & put it down to the poor condition of our roads (potholes especially) and the use of salt on our roads which increases corrosion rates
If broken then it is advisible to replace in pairs across the same axle
Let me know if you need anything else.
Best regards, Paul