Quote (Synonym @ Oct 19 2009 12:48am)
trang = poison skill dmg added
what does that have to do with anything?
All masteries from items (trangs, facets, whatever else gives +elemental type skill damage %) actually do work on equipment elemental damage.
A sorceress with maxed light mastery gets the boost to any light damage scs she may have in her inventory.
Likewise trangs works on poison charm damage. (this is as well why trangs gives a second boost to venom damage after the trang buffed skill has already been used to cast)
Although as sorowfulhatred pointed out elemental masteries do not work (despite lying character screen showing damage increase) on ranged attacks so its useless for this type of build. But not for the reason that you stated.