As anyone who plays this genre we all know that there are the basics that need to be covered and then the extras we would like to have. Personally I always cover the basics, one tank (warrior/barb), 1 healer obviously, 1 mage, and one rogue, and then generally one fun class which would cover a lock or bard or druid or something hybridy that gives me some options and flexibility.
But a 4 person party precludes at least for me the fun class. Basics have to be covered. I just think a 5th party member gives players the ability to refine a party instead of just covering the basics.
