Is it additive or multiplicative? I can't seem to find a reliable (recent) answer on Google. I'm reading something about it being bugged in grifts, is that still a thing?

its multiplicative and not only that, every member of the party profits from a ruby in a helm

say
4 players
only 1 with ruby
everyone gets more 39%(?) more xp

thats why XP geared chars are so popular this season, becuase they buff the XP for the whole group

I dont think that is how it works.

Iirc exp bonus % are averaged out for whole group.

This is to even out the unfair advantage one guy gets to hoard all exp by using only exp gears.

This post was edited by mewlad on Sep 30 2015 04:26am

That's exactly how it works just like TheGood said.

only 1 ruby in helm wont make any change, you need to have a full % build to Show signifiquance, like leo crown passive, leo ring + hellfire, cain set + born set as well

yes, it was just an example ofc

this.

Check this barb : http://us.battle.net/d3/en/profile/CALLMEOCT-1144/hero/66657896

this barbs got the wrong cains set the lev70 one gives 50% xp he also misses the borns weap with a gem of ease or at least rorg ring in cube for the 20%bonus ...

Signifiquance

He has 70 cains