the "/" implies an "or" in that instance. The Darklight Cuirass or a body w/ double melded crit materia's. An equivelant.
Also, I'd really like to know what the crit rate translates to in a % value. Wondering if the trade off is worth it, but considering rampage, I'd say War if anything is the best job to pursue a crit build in. Why else would they throw so much Crit rate nonsense in with this patch. When you get that gear setup, let us know how it works out !