If I was using a widow maker on a barb with a helm that had multiple jewels that provided different types of elemental damage cold fire lite would those stack or no

yes, but those ele dmg is low...

In PvP I’ve seen barbs use an Um’d Widowmaker besides that for pvm I prob wouldn’t. If you want elemental damage two gimmershreds and double throw pump out a decent amount of elemental damage.

they will stack but will not do significant damage.
if you have the charms in large amounts you could possibly use them on a bow sorc with mastery buffing them.

I currently have a bow/ww barb for pvp, I use half an inv of poison charms, it works alright until someone has anti poison gear.
trangs now boosts poison on guided

other elemental damage isnt going to be significant on barb though.