As we all know you get a bump in xp for doing a quest on Hard or Elite.
Most are well aware that the more people you have in a quest it scales up to include hires.
So the quest gets harder if you add more players (time goes down if your crew knows what to do and how to split)
but you do not get an increase in xp for having a full group.
I have seen a lot of posts about oh we can't get groups or fill pugs etc. Perhaps if there was an increase to the xp awarded for having a full group or a streak bonus for a group that stays togeather for a number of quests that might change.
They could do something like +5% for every quest after the 1st that a group runs togeather cap at +25%.
Or add 5/10/15% to groups of 2/4/6 not really sure raids should be included as they tend to be run with full groups.