Yep, group XP is split amongst nearby group members, and the XP should already be getting a bonus based on the group size. The current numbers are:
1 person: 100% of the monster's XP value
2 people: 125% total (split two ways)
3 people: 133% total
4 people: 150% total
5 people: 166% total
6 people: 175% total
7 people: 190% total
8-10 people: 200% total
So it's not a huge amount, but should be noticeable! Instead of further raising the percentages, I've been thinking there might be a support role in there, like the bard class might literally boost that XP group bonus, or something like that.
Only nearby group members count, so people that are far away from the combat shouldn't get a split (and shouldn't count towards the number of group members, above)."