I went home for lunch today to check out the rumor of increased xp bonus for solo and small groups.
Here is what I noticed.
Last night I spent time soloing on the beach of the Enchanted Lands, killing Salt Snappers. They are level 31 and 32 and con orange and red to me, respecively as a 27 ShadowKnight. Last night I was getting about a quarter of a percent each kill. It's a little slow, but I can kill 1 turtle every 3 minutes, the kill usually takes about 2 minutes, and I wait for my power and buffs to get ready in between kills. So 3 minutes on the dot. Doing this just by the numbers provided, I can get a level in 20 hours, not counting the 1% xp per 'turtle killing quest' I get (repeatable) from a halfling at the dock.
When I logged on over lunch today, the same turtles now give me half of a percent XP. That is double what I was getting before. So now, technically, I can finish off a level in half the time it took before. Still a daunting task, but not near as bad as before.
If someone were doing several quests while killing the mobs needed for those quests I am sure it could be cut down even further.
To conclude, what my findings indicate, is that killing orange and red mobs solo, for maybe 4 hours a day will get you 1 level ever 2.5 gaming session.
Results may varry, but to me that sounds pretty comparable to grouping xp.
P.S. - I think my numbers are about right, but I don't feel like breaking out a calculator atm, so if they aren't - too bad. =)