Mapache
Explorer
Actually, they'd have DR in 4 encounters a day, but their damage output would be so low it'd almost balance out, and you'd just have 4 really long encounters per day, not 4 encounters per day where the party whupped butt.
How about four hybrid striker-clerics? With the right picks, hybrid striker-leaders can put out as much non-daily damage as a full striker while doing about 60% of the work of a leader, including big flashy save-the-party dailies. I've played an Avenger-Cleric and a Ranger-Cleric, both in part because Moment of Glory is so good. I maintain that an all hybrid striker-leader party is pretty much the nuclear option of 4E, with one controller-leader for vaporizing minions and maybe a defender thrown in you really want one.