Some things i noticed messing around with 5 characters: Some fights, the 5th character will spawn outside the battle area. If they're an archer rogue or a mage they can still be effective, but melee would be screwed. Examples of this: the boss fight at the top of the mage tower, the Zevran Ambush, the Witherfang Fight. In the Witherfang fight, my rogue was able to unlock the door that separated her from the rest of the group, which was cool. The 5th character doesn't follow the rest of the group as closely and tends to lag back for some reason. This may be the reason for the 'battle lockout' issue. In the Fade boss fight, the 5th character wouldn't appear at all.