Reasons to Group or Raid

Advantages of a Raid

• Warleaders (the healing ones) and defilers become enormously effective being able to see health bars and use their group heal effectively.
• Coordinated focus fire from over a dozen creeps will kill many targets even when being massively healed
• Coordinated movement in a flowing battle reduces losses with stragglers
• Voice and /raidshout are "in your face (and ears)" communication methods to get everyone together on a plan and execute it.  Also when the situation shifts, communication is paramount to getting creeps to rally around the new threat
• BA's, wargs, and weavers coordinating together with cripples, hinders, and stuns can turn a running freep into a dead freep.