Double Frost is a great style and most Zerkers use it, however, the best way to fight is always try to use your chain styles. This is very effective and allows you to deal out stuns, bleeds, and hinders one after the other rather than hitting over and over with only one style. Also, I try to have my "you parry" style up and ready as this can be "styled" with a quick back-up into a no-opening required style such as "doublefrost". That way if you don't actually parry, you will get off the double frost instead. I have cut way back on my use of double frost since it was nerfed some time ago, but I feel that the use of combo styles makes up for it.
Hope this helps
Sij