I know sov or voll is really good at finding that kind of information, i been sitting here for 10 min trying to look for cap at deathly strike but can't find it, it should be at the place where 50% cap is. I just asked some people, some said it cap some said it doesn't.
Deadly Strike
This is a chance of doing double damage. This bonus is applied after skills such as Critical Strike and any other damage bonuses. Critical Strike (CS) and Deadly Strike (DS) exclude each other.
If you have a 33% Deadly Strike item, and 68% Critical Strike Skill the complete chance to get double damage is: