3-4 martial characters
Battlemaster fighter, ranged.
Berserker Barbarian, melee.
Valor Bard, melee.
War Cleric, flex.
I shouldn't have to elaborate.
If Bladesinger ever comes in an update or mod you can swap out the cleric.
You could elaborate on why you have a ranged fighter and a melee bard. A melee bard will never do as much damage as a fighter all else being equal. A bard wont match the HP of a fighter all else being equal. Most of the bard's offensive spells are ranged.
My regular party is a bard, Lae'zel, Karlach and Shadowheart. (I'm currently running with a party of six - a ranger and a wizard).