Tony Vargas
Legend
The ranger and cleric both have the potential to be competent in melee - if they gravitate towards the STR build options (this is not the time for an archer or 'lazer' cleric). The wizard can help take care of himself by going with the staff implement and a good CON, and should make sure he always has a close attack on tap, as he won't be able to count on keeping out of melee.
Leaders and Defenders are both very useful to the party, but thier powers also leverage the party, so the smaller the party, the less payoff you get from some defender power and many leader powers. A very small party can probably get by with only one or the other (or a bit of both in the form of a Paladin), or even neither, and just adopt less usual tactics (being all very sneaky/mobile, and being selective about which encounters you stand and fight, for instance).
Leaders and Defenders are both very useful to the party, but thier powers also leverage the party, so the smaller the party, the less payoff you get from some defender power and many leader powers. A very small party can probably get by with only one or the other (or a bit of both in the form of a Paladin), or even neither, and just adopt less usual tactics (being all very sneaky/mobile, and being selective about which encounters you stand and fight, for instance).