Leveling up all heroes to 10 is heavily recommend for every player. After that leveling is pointless, you only get pretty golden cards.

After max level has been reached by a hero, your hero is supposed to turn golden. However this feature is not implemented yet.

Leveling up all heroes to 10 is heavily recommend for every player.

After max level has been reached by a hero, your hero turns golden. This feature was implemented in Patch 1.0.0.4944.

Golden Heroes have been added and now can be unlocked after winning 500 Ranked games with a Hero! Track your progress on the deck selection screen in Ranked Mode.