A group of 2 halves the XP earned from kills. RAF triples the XP.
Example:
2 lvl 1 Nelfs kill a lvl 1 mob.
Normally this would be 50 XP solo.
Grouped per 2 this is reduced to 25 XP.
Then RAF kicks in and you get 75 XP.
So in fact you are getting triple XP for kills.