I think it would be a good idea to let us iron out issues with mid-level play as well given the things we've already discovered about low-level play.
If fireball can set 12 enemy combatants on fire, that's a problem.
If counterspell can only counter spells directed at you, that's a problem
If Haste allows you to cast two regular spells each round, that's a problem
There's quite a few things I'd like to make sure they get right with fifth level.
