Style of play varies wildly in and out of groups. It's very easy to hide behind a tank, do as your told and collect wild amounts of XP. The equipment worn and tactics used are often radically different.
I was more interested in the advantages and disadvantages of each class. For instance, if it was impossible for a cleric to level unless they were in a group, that would be a significant disadvantage. I don't know if that is the case though.