keterys's ideas on fixing the assassin are good (though it's worth noting that the OAssassin will typically be using a d12 weapon, not a d8 weapon).
Fixing the psionic classes: well, con for basics is a given. Regarding the math of psionic classess...why not:
Double base damage at epic (because...of course you should).
Double the cost of an augment each time it's used in an encounter.
Fix brokenly-scaling low level powers so they don't brokenly scale (just like brokenly scaling at wills from other classes have been fixed).
Vamps: I think they basically just need more damage to make them more exciting. But they're actually pretty OK to hybrid with now, I think, though the charisma hybrid could use a 1st or 5th level daily cha power.
Fixing the psionic classes: well, con for basics is a given. Regarding the math of psionic classess...why not:
Double base damage at epic (because...of course you should).
Double the cost of an augment each time it's used in an encounter.
Fix brokenly-scaling low level powers so they don't brokenly scale (just like brokenly scaling at wills from other classes have been fixed).
Vamps: I think they basically just need more damage to make them more exciting. But they're actually pretty OK to hybrid with now, I think, though the charisma hybrid could use a 1st or 5th level daily cha power.