Volatile armour grants about 5k physical and spell resist. It grants mitigation based on this formula;
(resistances - 100) / (66*10) for CP160 ---> (5k - 100)/660 = about 7.5% mitigation.
If you are a light armour wearer..... this wont even make a tiny little bit of difference cos quite a few builds out there can penetrate 15k resists. So LA typically provides like 10k resists. With volatile it would put u at about 15k. Which most builds will reduce to 0. You might be better off not even running volatile armour if you cannot hit the 20k mark in resists.