It might not be impossible to go without a cleric or a druid, but it will be very tedious. I have 2 clerics in my 8 person party (barbarian, monk, rogue, sorcerer, cleric, npc fighter, npc wizard, npc cleric) and I have to backtrack in the temple to rest far more often then I like. Without a healer you will be backtracking far far more often then me.
2 fighters and a barbarian is probably less than optimal. Partly because this game is more oriented towards large groups of less powerful enemies (rather than a couple very strong enemies) where area of effect spells and crowd control will help you more than the burliest warrior (a well placed area of effect or crowd control spell can eliminate 50% or more of your opponents in the same time your fighter is cutting down one person). Also you have to spread the magical equipment between 3 front line fighters. Finally warrior npcs are probably the most common and easily recruited npcs.
In my party the barbarian and npc fighter are the walls that block doorways and hallways keeping the rest of the party safe. The monk is the opportunity attacker who intercepts those who make it past the barbarian and fighter or kills enemies who are near death. The rogue waits for an enemy who is already engaged and attacks for sneak attacks. The cleric is back up for the barbarian and npc fighter and secondary emergency healer. The wizard drops crowd control and the sorcerer drops area of effect damage. Npc cleric is an archer (martial weapons profiency-bow) and primary battle healer.
If I were playing with your party I would take cleave and great cleave for the fighters and barbarian. The wizard would probably memorize spells that effect multiple enemies rather than spells that are strong, but only effect one enemy.
Also if you recruit any npcs recruit a druid or a cleric. (if you are using the circle of eight mod Ronald is an easy cleric to recruit).
