Re: A Party of Strikers.
Blackguards are even easier then the Swordmage PMC stuff you were going through... Human, pick Ardent Strike as your extra at-will. Now you have both mark and punishment. Alternatively, Hybrid Blackguard with Warlock/Executioner and choose both Ardent Strike and Virtuous Strike, and then you can get some of the mass sanctioning encounter/dailies from your paladin side.
Needless to say, defender's covered. Leader on the other hand...