I think it would be cool to have an area or quest where you could practice fighting and tactics. The idea is you and/or your party enter an arena, talk to the "Arena Master" NPC to set up the type and numbers of monsters to spawn, and then fight.
There should be 2 modes:
- Practice Mode - where there is no xp penalty for dying and no xp gained
- Gladiator Mode - where you get xp based on the degree of difficulty of the match and where the full effects of death are on. The degree of difficulty could be based on level, numbers in the party, and equipment, etc.
This would allow people to try out new strategies, learn how to fight specific kinds of monsters, practice team tactics, see how different types of weapons compare, etc.
Just a thought.