What's the best team line-up?

If you have six natural 5 star heroes, these would be the best to use. By natural 5 star heroes, we mean ones that can only be acquired as five star heroes, not evolved into 5 star heroes.

Then thinking about the positions of your heroes, you should have a tank in the main slot in the first row and another tank/high damage hero in the fist slot of the back row. Put your main damage dealer in the second slot of the first row, and fill the rest of the slots with your best cards.

It's often the case that of the front row, usually only the first slot get's hit, and in the back rwo the same.