Re: A Party of Strikers.
Defender-easiest way is to be a blackguard, retrain to get ardent strike, then just pick divine sanction powers. You can hybrid to get warlock debuff powers if you want.
Controller, rogue and monk both have plenty of controller leaning powers. Minion popping is a controller trait, best accomplished by AoE damage, but to kill a minion 2 damage is overkill. Slap sorcerer onto one of the above to get more popping powers. Warlocks are great single target controllers as mentioned, but a few sorcerer powers don't hurt.
Leader-Again, the warlock has something for everything. A Thaneborn barbarian hybrid Sorcerer-King Warlock would probably be your best bet, MC Bard heavily to get Cha heals. Ardent might work too, not as familiar with that class.