In our two 4e campaigns up to this point, group compositions were:
Game 1: 3xStriker, 1xLeader, 1xDefender
Game 2:
Initial group: 2xStriker,1xLeader,1xController,1xDefender
Then the Leader was killed:
Group 2: -1xLeader, +1xController
Then one of the Controllers was killed:
Group 3: -1xController, +1xLeader
Then we had a near TPK(everything but 1xStriker died):
Group 4: 2xStriker,1xLeader,1xController,1xDefender
Then the new Controller died:
Group 5(current): 3xStriker,1xLeader,1xDefender
Edit:
We also have a pick-up game with a variable amount of players, randomly selected character classes, and a high fatality rate.
Initial group: 1xStriker,1xLeader,1xDefender
Striker and Leader died in the first fight:
Group 2: 1xLeader,1xController,1xDefender
The Defender went from full health to negative bloodied in 1 round vs and elite:
Group 3: 1xLeader,1xController,1xDefender
The new group lasted until level 2, then TPKd(and we picked up a new player):
Group 4: 2xLeader,2xDefender
The new group actually kicks ass. We all focused on DPS as much as possible, since with 1 Shaman, 1 Cleric, and a Paladin, we have healing pretty much covered. Surprisingly solid, decent DPS, extreme-durability group.