Please clarify your goal.
If all you want is a character that is going to successfully quest, then just about any class combo can be successful. Some better than others; Reynmar's suggestion of Warden/Druid is a good one, they have a white hit similar to the Knight/Mage, so set up correctly can do massive damage. I personally like Warrior/Druid mainly because you can swap to Druid/Warrior for runs if the buff is needed.
Endgame instances...well the only one I can think of is a Knight/Priest though it is not the top tank it has some decent abilities; but, questing in PvE can be boring. I have heard people say that Champion/Priest makes a good tank, but I have never seen one in action so cannot speak to it.