Umbraal wrote:

Perhaps that in order to shatter, the original time of a freeze needs to have a threshold higher than the threshold for freezing.

This is already the case. You need to actually freeze the thing, meaning you need to deal enough cold damage proportionally to their life to create a freeze of at least 300ms.

However, confirming this allowed me to find a small bug whereby chills would not apply to already-frozen enemies (they should do so, because they'll probably last long enough to still be there after the freeze ends).

Bulkathos wrote:

Does attack speed effect how fast you put traps or i need cast speed ?

Neither, you need Trap Laying Speed.