Last night was a pain in the @$$ all due to the way you accrue XP in the game. Here's what I've discovered about groups just from personal experience:
If you have high levels mixed with low levels and fight high level villains – the low level people get little to no XP.
If you have high levels mixed with low levels and fight low level villains – the high level people get little to no XP.
The way around it is to SK ALL of the low level people and not to play with a varied group of levels – i.e. 7-24. If we want to level fast we will all need to play similar level characters, SK any low level people and fight hard and fast. The best thing to do is to go to a hazard zone (Boom, Faultline, Perez) or do missions of the higher level people (u get bonus xp at end of missions). I’m guessing that the difference in levels should not exceed 3 levels difference in characters, barring SK’s. Meaning we should travel unSK’ed with no one 3 levels lower or higher than yourself.
XP chart
http://faqs.ign.com/articles/539/539615p1.html
Decent site for coh stuff, maps etc.
http://coh.warcry.com/