Sorry to see you go CaBaNa! I hope you do have time for many more adventures in the future. Let me know before the start of this adventure if your schedule magically clears
The information posted in the first post is (mostly) accurate, other than CaBaNa has dropped out. I will see by the end of the week who still has their submissions outstanding and go from there.
While it would be nice to have a defender, one of the good parts of 4e is that it's not technically required. There's enough healing to go around from the character lists, and with two controllers (and one hybrid), the damage dealing from the monsters should be kept to a minimum.
Also, I like to tune encounters to groups, not the other way around. In my RL D&D game, I play a bear shaman and we don't really have a defender (the warrior sort of counts, but we mostly make him break open doors and set off traps). I'll experiment and see what happens.